Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

10" Dob Needs What?

  • Please log in to reply
35 replies to this topic

#1 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 23 May 2020 - 03:34 AM

 I'm going to be getting a dob soon. Orion Skyquest 10" f/4.7 and I've been reading some of the post about coma correctors and Parrcore. Am I going to need all of that for my images to look decent? I'm am going to be using the scope for visual observing only and my last dob was an 8" Skyquest. I wasn't able to get my images of Jupiter to be sharp and show contrast and the Great Red Spot. Just very tiny, fuzzy Jupiter. All I had at the time is a 3x barlow and the two plossls that came with the scope. Do you think I need a major upgrade in my eyepieces, and a coma corrector?? What do you think? I'm going to be using it for DSO too. I live about 3 miles outside of a small city and the neighborhood has light pollution. I'm going to be observing in my backyard that has no grass just creek pebble cause my mom didn't want to mow the backyard. undecided.gif I'm planning on getting a few Naglers and other eyepieces. I don't know how to use a Telrad so I was going to replace the finder scope with one that shows correct image. I'm also going to be studying nebulas and galaxys. I want as many people as possible to give their suggestions. This is going to be a life long marriage and I want my scope to show it's stuff.


  • aeajr likes this

#2 stevenrjanssens

stevenrjanssens

    Vostok 1

  • -----
  • Posts: 158
  • Joined: 24 May 2018
  • Loc: Vancouver, BC

Posted 23 May 2020 - 04:38 AM

If this is a lifelong project, then you don't need to figure everything out today. To get going all you'll need are the tools to star hop and a minimum set of eyepieces to get you started. Before getting a coma corrector, I would use the scope and see if the coma bothers you.

 

To star hop, a Telrad, a right-angle correct-image finder and a low power eyepiece are all worth having, along with good star charts. I believe your scope comes with a red dot sight. The benefit of a Telrad is its rings can be used under dark enough skies with enough naked eye stars to align the scope directly on the target. But the red dot sight should work for the time being to get aligned on the first star and then you can star hop with the eyepiece. I typically go straight from my Telrad to my 24mm Panoptic to star hop and leave my RACI finder untouched. For star charts, I can't recommend Sky Safari enough. You can overlay FOVs of all your eyepieces and change the mag limit on stars to match your conditions.

 

For eyepieces, try and a get a set that gives you roughly 4mm, 2mm and 1mm exit pupils, which gives low, medium and high power. Exit pupil = telescope aperture / magnification = eyepiece focal length / telescope f-ratio. In your scope this would be roughly 5mm, 10mm and 20mm—I use 7mm, 13mm, and 24mm in my F/5 (F/5.75 with Paracorr). Just make sure your low power eyepiece yields a true field of view of at least a degree, anything less might make star hopping a bit tedious.


  • ShaulaB likes this

#3 sg6

sg6

    Cosmos

  • *****
  • Posts: 7,710
  • Joined: 14 Feb 2010
  • Loc: Norfolk, UK.

Posted 23 May 2020 - 06:29 AM

Reality is that you will need decent eyepieces and maybe in time a coma corrector.

Eyepieces since at f/4.7 you are into or entering the area where the eyepieces have to be able to handle a fast scope, and like all else that costs.

 

Coma corrector is a "maybe" some people are not bothered by a slightly "fuzzy" edge, others want perfection across the field. Principal here is the object should be in the central area and that should be good anyway. So that can wait

 

The eyepieces you will in many ways want soon.

 

Have heard Paradigms work to f/4.5, and although I have a set and I like them I suspect that is more a case of where they basically give up. So f/5 maybe. Means they could be out of consideration.

 

I do not know about the X-Cel LX's or the Meade HD. X-Cels I would say match Paradigms, HD's may be a little better - only may. All I suggest are boarderline at f/4.7

 

Leaves then ES. Probably a better match to the scope. Your focal length will be 1200mm. So wide is the almost standard 24mm 68 degree one. 50x and around 1.4 degree view.

 

Mid power say 80x is 15mm - problem is 16mm 68 degree for 75x and 0.9 degree view , or, 14mm 82 degree for 86x and 0.96 degree view? The 68 costs a bit less, but not a lot less.

 

High end is likely the 6.7mm 82 degree for 179x and 0.45 degree view.

I would still say the 8.8mm may be better all round however, 136x and 0.6 degree view.

 

Jupiter should be good in either mid power options and Saturn in the either high option.

Moon is easy all round and Mars is a pain all round. I don;t care about Mars but every 2 years there is the wails of anguish from astronomers trying to see detail. Consider Mars a bit "specialist" as a target.

 

Seems you need 250x and more for anything, that tends to be both difficult and rare as scope, eyepiece and atmosphere all need to be on your side. But Mars is October-November time, just wait and decide.

 

So in summary: 24mm/68, then 16mm/68 or 14mm/82, then 6.7mm/82 or 8.8mm/82.

So that is minimum of 3 and guess around $400.

At a guess you will eventually get both 6.7mm and 8.8mm lol.gif  lol.gif  lol.gif and equally likely the 4.7mm (everyone does)


Edited by sg6, 23 May 2020 - 06:30 AM.

  • 7Soeurs likes this

#4 earlyriser

earlyriser

    Surveyor 1

  • *****
  • Posts: 1,841
  • Joined: 08 Nov 2016
  • Loc: Cincinnati

Posted 23 May 2020 - 07:00 AM

What do you use to collimate your scope? 



#5 gwlee

gwlee

    Surveyor 1

  • *****
  • Posts: 1,880
  • Joined: 06 Sep 2015
  • Loc: 38N 120W

Posted 23 May 2020 - 09:23 AM

If it’s a new scope, it comes with everything you need to get started. Suggest just using it for a while to see how it works for you before buying anything else. 


  • ShaulaB and havasman like this

#6 wavelandscott

wavelandscott

    Mariner 2

  • -----
  • Posts: 203
  • Joined: 23 Jan 2008
  • Loc: Ridgefield, Connecticut, USA

Posted 23 May 2020 - 10:12 AM

Adjustable height chair...quality tool(s) to collimate 


  • lsfinn, havasman and vdog like this

#7 Napp

Napp

    Vanguard

  • *****
  • Posts: 2,052
  • Joined: 26 Jul 2015
  • Loc: Florida, USA

Posted 23 May 2020 - 10:41 AM

What are your expectations concerning Jupiter?  The planets are small in a scope.  Yes better optics help with resolution but earth’s atmosphere has the final say in how clear the image is.  Even with a larger scope 200-250X is going to be the limit on most nights.  There are nights my 16 inch is limited to 150X without turning Jupiter into mush.  For now the planets aren’t that high in the sky for the northern hemisphere anyway which means their light has to traverse even more of earth’s atmosphere.  Yes, most of us have short focal length eyepieces waiting for those incredibly rare times the atmosphere is still enough we can crank up the power in the planets.  But those nights almost never come - unless maybe you live somewhere out west in the high desert.  Seeing the red spot and cloud bands on Jupiter has more to do with contrast.  Some filters may help.  There are a lot of opinions in the forums about which work better or even if they do.  The results are subtle at best.  Time at the eyepiece will probably make the most difference.  



#8 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 23 May 2020 - 10:54 AM

What do you use to collimate your scope? 

I have a cheshire but I don't know how to use it so I use the collimate cap that comes with the scope.



#9 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 23 May 2020 - 10:57 AM

What are your expectations concerning Jupiter?  The planets are small in a scope.  Yes better optics help with resolution but earth’s atmosphere has the final say in how clear the image is.  Even with a larger scope 200-250X is going to be the limit on most nights.  There are nights my 16 inch is limited to 150X without turning Jupiter into mush.  For now the planets aren’t that high in the sky for the northern hemisphere anyway which means their light has to traverse even more of earth’s atmosphere.  Yes, most of us have short focal length eyepieces waiting for those incredibly rare times the atmosphere is still enough we can crank up the power in the planets.  But those nights almost never come - unless maybe you live somewhere out west in the high desert.  Seeing the red spot and cloud bands on Jupiter has more to do with contrast.  Some filters may help.  There are a lot of opinions in the forums about which work better or even if they do.  The results are subtle at best.  Time at the eyepiece will probably make the most difference.  

I would like to see Jupiter with the Great Red Spot and not so tiny and fuzzy.


  • Simoes Pedro likes this

#10 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 23 May 2020 - 11:02 AM

Adjustable height chair...quality tool(s) to collimate 

From my last experience with a dob, that would be a necessity. I got tired of standing pretty quick. Can you suggest one? I'm a pretty hefty gal at 223lbs. undecided.gif Yeah, okay so I like donuts and Starbucks.



#11 vdog

vdog

    Surveyor 1

  • *****
  • Posts: 1,589
  • Joined: 30 Aug 2018
  • Loc: California Central Valley, U.S.A.

Posted 23 May 2020 - 11:10 AM

Adjustable height chair...quality tool(s) to collimate 

+1 waytogo.gif  I use a version of the Starbound observing chair, but there are other choices.

 

I would also consider the Meade UWA 5.5 for Jupiter, currently on sale for $99.  That's about the perfect magnification for Jupiter in my 10" f/4.7.   Works pretty well on Saturn too.

 

And, if budget allows, a Baader Moon & Skyglow filter really helps bring out the red in the Great Red Spot.
 


Edited by vdog, 23 May 2020 - 11:12 AM.


#12 Napp

Napp

    Vanguard

  • *****
  • Posts: 2,052
  • Joined: 26 Jul 2015
  • Loc: Florida, USA

Posted 23 May 2020 - 11:22 AM

I know the 8 inch Skyquest came with a 25mm ep.  I’m guessing the other was a 10mm ep.  With a 1200mm focal length you were getting 48X and 120X respectively.  A 3X barlow would have turned those into 144X and 360X.  It’s very unlikely that 360X would yield more than a fuzzy blob.  Usually the best you can hope for is 200-250X.  So, prepare yourself.  The image is not going to be any bigger in the new scope.  10 inches over 8 inches isn’t going to make a lot of difference in resolution either.  Better quality eyepieces and picking the nights you observe will help with resolution if you don’t try to use too much magnification for conditions.  And forget the barlow.  Get a good quality eyepiece somewhere in the range of 4.7-6mm.  Also a good quality ep in the range of 9-11mm.  For the crispest views on the average night you will use the 9-11mm more anyway.  Jupiter does not show as much contrast as you see in pictures.  A filter can help the red spot stand out better.  The Badger Contrast Booster is good.  You want to observe when the stars in the vicinity of the planet are hardly twinkling.  Planetary observing takes time and patience at the eyepiece.  You are trying to catch those magic moments when earth’s atmosphere calms enough that planetary features pop.  



#13 havasman

havasman

    Voyager 1

  • ****-
  • Posts: 10,813
  • Joined: 04 Aug 2013
  • Loc: Dallas, Texas

Posted 23 May 2020 - 12:35 PM

It's likely that the reason your images of Jupiter and Saturn are less crisp than they should be is that your collimation is not spot on. Collimation enables everything in a Newtonian system to work as it should. Whatever tools you decide on must be correctly used. If you have instructions for your Cheshire, study them until they make sense and give it a shot again. If not, these Astrosystems tools work and are relative bargains - https://www.eyepiece...OLS_s/1859.htm 

 

Your XT10 will very certainly give you crisp sharp images of the major planets and the GRS will be easily seen. I have one. You should see tints in the big planet's bands and on really good nights, features within the bands. Saturn will show pale pastel tints to the bands as well as gaps in and shadows of the rings. But you have to get the mirrors aligned.

 

Clear and crisp is more important than magnification. I regularly observe DSO's at 400x and more with a 16" Starmaster but, as above, very seldom use > 250x for planetary observing. Your new 10" aperture will give you a bright planet from which your observing skill will pull details.

 

Coma corrector? I used my XT10i a couple of years w/o one. Then one night I stuck one in the focuser and had one of those WOW moments when I saw the field cleared of coma. The Astro-Tech coma corrector from Astronomics works very well in an XT10 and costs much less than a Paracorr.

 

Eyepieces? Yep, that's a slippery slope for sure. At f4.7 your scope presents a more sloped set of light rays to the eyepiece than a slower scope and benefits from more complex eyepiece designs that are designed to put those rays to parallel when they go to your eye. Bending light in glass creates aberrations. Complex designs minimize those via glass and coatings combinations. What's your budget? There was an ES82 18mm that sold on Astromart for $180 that is just excellent in an XT10. Shopping the classifieds will save you $$$. The ES82's are very good and can be best buys on the secondary markets.

 

Chairs? Starbound is #1. Plans for a Denver chair can be googled and built from cheaper lumber.


Edited by havasman, 23 May 2020 - 12:39 PM.

  • ShaulaB likes this

#14 aeajr

aeajr

    Voyager 1

  • *****
  • Posts: 13,673
  • Joined: 26 Jun 2015
  • Loc: Long Island, New York, USA

Posted 23 May 2020 - 01:10 PM

 I'm going to be getting a dob soon. Orion Skyquest 10" f/4.7 and I've been reading some of the post about coma correctors and Parrcore. Am I going to need all of that for my images to look decent? I'm am going to be using the scope for visual observing only and my last dob was an 8" Skyquest. I wasn't able to get my images of Jupiter to be sharp and show contrast and the Great Red Spot. Just very tiny, fuzzy Jupiter. All I had at the time is a 3x barlow and the two plossls that came with the scope. Do you think I need a major upgrade in my eyepieces, and a coma corrector?? What do you think? I'm going to be using it for DSO too. I live about 3 miles outside of a small city and the neighborhood has light pollution. I'm going to be observing in my backyard that has no grass just creek pebble cause my mom didn't want to mow the backyard. undecided.gif I'm planning on getting a few Naglers and other eyepieces. I don't know how to use a Telrad so I was going to replace the finder scope with one that shows correct image. I'm also going to be studying nebulas and galaxys. I want as many people as possible to give their suggestions. This is going to be a life long marriage and I want my scope to show it's stuff.

Congratulations on the new scope.  I had an XT8i, optically the same as your XT8.  Really liked it.   

 

Above you talk about an XT8, but your signature says you have a 6" reflector.  Is that a typo?

 

Point by point on the bolded items.

 

Expectations, what are your expectations?  Planes will never look like the pictures in the magazines when you are viewing through an eyepiece in a 10" scope.   Those are produced by astrophotography based on light accumulated over time, which your eyes can't do. 

 

 

Blurry images and altitude - The sharpness of the image of any planet or deep sky object depends a LOT on the atmospheric conditions.  If you are viewing planets below 30 degrees altitude you are looking through a LOT of atmosphere which will cause the image to blur and drift in and out of focus. This has nothing to do with your eyepieces or your telescope.  Eyepieces and aperture can not fix this.

 

What is SEEING and why it can be bad.  This is not a problem with your  telescope
http://www.skyandtel...ing-the-seeing/
http://www.damianpeach.com/seeing1.htm
http://www.damianpea...m/pickering.htm
 

 

Too much mag - Another cause of blurry images is applying too much magnification. The XT8 has a 1200 mm FL and came with a 25 mm and 10 mm Plossl. From my location on Long Island, outside of NYC, many nights I could not get above 180x without significant degradation of the image.  

 

In the XT8, 25 mm gives you 48X. In a 3X barlow that gives you 144X - generally workable at my location for targets above 30 degree altitude

 

In the XT8 10 mm gives you 120X.  In a 3X barlow that is 360X with is unlikely to be useful on anything other than the Moon.  Put Jupiter in that and it will be a blurry mess.

 

Naturally there are very good Barlows and there are crap Barlows.  I don't know what you have.

 

Under very good conditions I have viewed Jupiter in the XT8 at about 300X.  I think that was in June of 2017 and Jupiter was almost 40 degrees high.  Over the 4 years I had the scope and hundreds of observing sessions, I think I was able to do that 6 times.   That was extraordinary conditions combined with Jupiter being high in the sky. 

 

In general, more aperture will allow you to apply more magnification, but can still be restrained by atmospheric conditions.  My 12" Dob allows me to apply about 40 to 70X more mag to an image than my 8" did.  But the 12" gathers 2.25X as much light.  Your 10" will gather about 77% more light than the 8" so don't expect a huge leap.

 

Overall, with my XT8, I rarely took mine over 230x and 180X was often as high as I could go. 

 

Image Size - This is strictly related to magnification.  100X is 100X and produces the same size image in any telescope.  The larger the aperture, in general, the better the quality of the image.

 

Great Red Spot - I have viewed the GRS in my 80 mm refractor at 100X and my 127 mm Mak at 150X.  It looked better in my XT8 at 200X.   Have not seen it yet in my Apertura AD12 yet.  Waiting for later in the season.

 

 

Observing Saturn

https://telescopicwa...th-a-telescope/

 

Observing Jupiter

https://telescopicwa...gh-a-telescope/

 

 

Eyepieces - Overall the Plossl eyepieces that came with the XT8 are pretty good eyepieces.  Sharp with good correction.  People don't replace them because they are bad, they replace them because they want a wider field of view.  But Orion Plossls are very good planet viewing eyepieces.   Having said that, I have replaced mine mostly with Meade and Explore Scientific 82 degree eyepieces.  And I use my Baader Hyperion 8-24 zoom more than any other eyepiece.

 

Understanding Telescope Eyepieces- There are recommendations, based on budget,
but the meat of the article is about understanding the considerations and specifications
to know when selecting eyepieces.
https://telescopicwa...cope-eyepieces/

 

Coma Corrector - This basically cleanse up the edge distortions that a low focal ratio scope will experience.  I don't think it will do much for the center 60% of the image.  Good thing to have but I don't think it will address your concerns.

 

 

Collimation - You must properly collimate a Newtonian scope.  This is a skill you must develop and gain confidence.  If you scope is poorly collimated then your images will be poor.  

 

The Defocused Star test of collimation - use your 10 mm eyepiece for this.  If you pick a bright star, center it and then defocus it you should get a dark area in the center with a concentric ring or rings around it.  As long as it is even all around your are in good collimation.  I do this at the start of every observation session.   If the image is off center then I know I need to do a collimation procedure on my scope.   I can use the scope tonight if I wish but it needs adjustment.  I just might not get the best views I could possibly get.
https://www.youtube....h?v=FrpldHJFABo

 

How to Collimate an Orion Reflector Telescope using a collimation cap or a laser
https://www.youtube....h?v=YAVGcGEBmCE

 

Light Pollution - Galaxies and Nebula - To really view these you need a dark location.  You need a dark sky so there is contrast between these faint objects and the background sky.  Aperture will not solve this issue.  And  you need a dark ground area so your eyes can dark adapt.

 

Light Pollution
https://telescopicwa...ight-pollution/

 

Filters - To really explore nebula you will want a selection of filters.

 

Understanding Filters
https://telescopicwa...escope-filters/

 

 

Bottom line is I don't really know if the issue is your equipment, how you are using it or your expectations.  If you expect the image to look like what is in the magazines, you will never be satisfied.  If that is the case, get a good equatorial mount, an imaging camera, an 80 mm APO refractor and take up astrophotography.  About $2500 should get you started. 

 

 

I hope this helps. 


Edited by aeajr, 23 May 2020 - 01:18 PM.

  • PatrickVt likes this

#15 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 23 May 2020 - 01:11 PM

It's likely that the reason your images of Jupiter and Saturn are less crisp than they should be is that your collimation is not spot on. Collimation enables everything in a Newtonian system to work as it should. Whatever tools you decide on must be correctly used. If you have instructions for your Cheshire, study them until they make sense and give it a shot again. If not, these Astrosystems tools work and are relative bargains - https://www.eyepiece...OLS_s/1859.htm 

 

Your XT10 will very certainly give you crisp sharp images of the major planets and the GRS will be easily seen. I have one. You should see tints in the big planet's bands and on really good nights, features within the bands. Saturn will show pale pastel tints to the bands as well as gaps in and shadows of the rings. But you have to get the mirrors aligned.

 

Clear and crisp is more important than magnification. I regularly observe DSO's at 400x and more with a 16" Starmaster but, as above, very seldom use > 250x for planetary observing. Your new 10" aperture will give you a bright planet from which your observing skill will pull details.

 

Coma corrector? I used my XT10i a couple of years w/o one. Then one night I stuck one in the focuser and had one of those WOW moments when I saw the field cleared of coma. The Astro-Tech coma corrector from Astronomics works very well in an XT10 and costs much less than a Paracorr.

 

Eyepieces? Yep, that's a slippery slope for sure. At f4.7 your scope presents a more sloped set of light rays to the eyepiece than a slower scope and benefits from more complex eyepiece designs that are designed to put those rays to parallel when they go to your eye. Bending light in glass creates aberrations. Complex designs minimize those via glass and coatings combinations. What's your budget? There was an ES82 18mm that sold on Astromart for $180 that is just excellent in an XT10. Shopping the classifieds will save you $$$. The ES82's are very good and can be best buys on the secondary markets.

 

Chairs? Starbound is #1. Plans for a Denver chair can be googled and built from cheaper lumber.

Collimation?? That could've been the problem in the 8" dob I had. I got my scope on a snowy day and my then hubby and I put it together. I read the instructions for collimation of the secondary and primary mirrors. I decided to line up the secondary mirror first. I got it so out of alignment that when I got it back in, I don't know if I got it to where it should be. Only did I find out later that the secondary mirror rarely needs to be adjusted. I lined up the primary and took it out. The stars were crisp and big. I even saw a meteor enter the atmosphere. But that was the extent of my flawless observing. The planets were as I said. I saw Saturn and its rings. So tiny I could barely make it out. Mars was just a pinpoint of light, so was Venus. I was disappointed. Jupiter was just as I described it. Fuzzy ball of grey with two darker bands.



#16 gwlee

gwlee

    Surveyor 1

  • *****
  • Posts: 1,880
  • Joined: 06 Sep 2015
  • Loc: 38N 120W

Posted 23 May 2020 - 01:26 PM

A 10” will give you 23% more aperture and resolution than your 8”, so the difference on the details you can see on Jupiter will be noticeable, but not dramatic in side by side testing. 

 

I use an inexpensive 8” Dob for observing Jupiter, and it works well. The biggest issues that can detract from Jupiter views are scope cooling, scope collimation, and seeing conditions. Cooling and collimation requirements are more exacting for a 10” f5. 

 

Taking full advantage of the 10’s greater aperture will depend on learning to properly cool it, collimate it, and learning to recognize and address seeing conditions more than anything else, so recommend mastering these skills before buying more accessories.

 

However, learning to star test is very helpful for evaluating seeing conditions, and for confirming that the scope is well collimated and well cooled. For this scope, you will probably want to use an eyepiece around 5mm for star testing, and it will give excellent views of Jupiter when the seeing conditions are good enough to support viewing at 240x. 



#17 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 23 May 2020 - 01:35 PM

Congratulations on the new scope.  I had an XT8i, optically the same as your XT8.  Really liked it.   

 

Above you talk about an XT8, but your signature says you have a 6" reflector.  Is that a typo?

 

Point by point on the bolded items.

 

Expectations, what are your expectations?  Planes will never look like the pictures in the magazines when you are viewing through an eyepiece in a 10" scope.   Those are produced by astrophotography based on light accumulated over time, which your eyes can't do. 

 

 

Blurry images and altitude - The sharpness of the image of any planet or deep sky object depends a LOT on the atmospheric conditions.  If you are viewing planets below 30 degrees altitude you are looking through a LOT of atmosphere which will cause the image to blur and drift in and out of focus. This has nothing to do with your eyepieces or your telescope.  Eyepieces and aperture can not fix this.

 

What is SEEING and why it can be bad.  This is not a problem with your  telescope
http://www.skyandtel...ing-the-seeing/
http://www.damianpeach.com/seeing1.htm
http://www.damianpea...m/pickering.htm
 

 

Too much mag - Another cause of blurry images is applying too much magnification. The XT8 has a 1200 mm FL and came with a 25 mm and 10 mm Plossl. From my location on Long Island, outside of NYC, many nights I could not get above 180x without significant degradation of the image.  

 

In the XT8, 25 mm gives you 48X. In a 3X barlow that gives you 144X - generally workable at my location for targets above 30 degree altitude

 

In the XT8 10 mm gives you 120X.  In a 3X barlow that is 360X with is unlikely to be useful on anything other than the Moon.  Put Jupiter in that and it will be a blurry mess.

 

Naturally there are very good Barlows and there are crap Barlows.  I don't know what you have.

 

Under very good conditions I have viewed Jupiter in the XT8 at about 300X.  I think that was in June of 2017 and Jupiter was almost 40 degrees high.  Over the 4 years I had the scope and hundreds of observing sessions, I think I was able to do that 6 times.   That was extraordinary conditions combined with Jupiter being high in the sky. 

 

In general, more aperture will allow you to apply more magnification, but can still be restrained by atmospheric conditions.  My 12" Dob allows me to apply about 40 to 70X more mag to an image than my 8" did.  But the 12" gathers 2.25X as much light.  Your 10" will gather about 77% more light than the 8" so don't expect a huge leap.

 

Overall, with my XT8, I rarely took mine over 230x and 180X was often as high as I could go. 

 

Image Size - This is strictly related to magnification.  100X is 100X and produces the same size image in any telescope.  The larger the aperture, in general, the better the quality of the image.

 

Great Red Spot - I have viewed the GRS in my 80 mm refractor at 100X and my 127 mm Mak at 150X.  It looked better in my XT8 at 200X.   Have not seen it yet in my Apertura AD12 yet.  Waiting for later in the season.

 

 

Observing Saturn

https://telescopicwa...th-a-telescope/

 

Observing Jupiter

https://telescopicwa...gh-a-telescope/

 

 

Eyepieces - Overall the Plossl eyepieces that came with the XT8 are pretty good eyepieces.  Sharp with good correction.  People don't replace them because they are bad, they replace them because they want a wider field of view.  But Orion Plossls are very good planet viewing eyepieces.   Having said that, I have replaced mine mostly with Meade and Explore Scientific 82 degree eyepieces.  And I use my Baader Hyperion 8-24 zoom more than any other eyepiece.

 

Understanding Telescope Eyepieces- There are recommendations, based on budget,
but the meat of the article is about understanding the considerations and specifications
to know when selecting eyepieces.
https://telescopicwa...cope-eyepieces/

 

Coma Corrector - This basically cleanse up the edge distortions that a low focal ratio scope will experience.  I don't think it will do much for the center 60% of the image.  Good thing to have but I don't think it will address your concerns.

 

 

Collimation - You must properly collimate a Newtonian scope.  This is a skill you must develop and gain confidence.  If you scope is poorly collimated then your images will be poor.  

 

The Defocused Star test of collimation - use your 10 mm eyepiece for this.  If you pick a bright star, center it and then defocus it you should get a dark area in the center with a concentric ring or rings around it.  As long as it is even all around your are in good collimation.  I do this at the start of every observation session.   If the image is off center then I know I need to do a collimation procedure on my scope.   I can use the scope tonight if I wish but it needs adjustment.  I just might not get the best views I could possibly get.
https://www.youtube....h?v=FrpldHJFABo

 

How to Collimate an Orion Reflector Telescope using a collimation cap or a laser
https://www.youtube....h?v=YAVGcGEBmCE

 

Light Pollution - Galaxies and Nebula - To really view these you need a dark location.  You need a dark sky so there is contrast between these faint objects and the background sky.  Aperture will not solve this issue.  And  you need a dark ground area so your eyes can dark adapt.

 

Light Pollution
https://telescopicwa...ight-pollution/

 

Filters - To really explore nebula you will want a selection of filters.

 

Understanding Filters
https://telescopicwa...escope-filters/

 

 

Bottom line is I don't really know if the issue is your equipment, how you are using it or your expectations.  If you expect the image to look like what is in the magazines, you will never be satisfied.  If that is the case, get a good equatorial mount, an imaging camera, an 80 mm APO refractor and take up astrophotography.  About $2500 should get you started. 

 

 

I hope this helps. 

I don't expect the views of Jupiter is be magazine perfect. I know it won't be and yes I know Hubble has spoiled us all with the view it gives. But I was hoping that Jupiter would be a little bit bigger than this > O. I had the 8"XTi too but I never used the computerized finder.



#18 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 23 May 2020 - 01:55 PM

A 10” will give you 23% more aperture and resolution than your 8”, so the difference on the details you can see on Jupiter will be noticeable, but not dramatic in side by side testing. 

 

I use an inexpensive 8” Dob for observing Jupiter, and it works well. The biggest issues that can detract from Jupiter views are scope cooling, scope collimation, and seeing conditions. Cooling and collimation requirements are more exacting for a 10” f5. 

 

Taking full advantage of the 10’s greater aperture will depend on learning to properly cool it, collimate it, and learning to recognize and address seeing conditions more than anything else, so recommend mastering these skills before buying more accessories.

 

However, learning to star test is very helpful for evaluating seeing conditions, and for confirming that the scope is well collimated and well cooled. For this scope, you will probably want to use an eyepiece around 5mm for star testing, and it will give excellent views of Jupiter when the seeing conditions are good enough to support viewing at 240x. 

When I view Jupiter it is located one hand's width from the top of the trees (my guess is that the trees are 2 miles away) from the horizon. I live in a neighborhood with the houses 5 feet apart. They do this because they get more money if they cram the houses together. So heat from the end of the day is still rising at 10pm. I go out at 9 or 9:30pm to set up, takes me a few minutes. And give the fanless scope about an hour to cool down. I use the 3x barlow but I decided to scrap the barlow because it could be too much magnification. So if anyone out there wants a Orion 3x barlow, let me know and I'll send it your way for free. I'm going to get a Shorty 2x.


Edited by stargazer32864, 23 May 2020 - 01:58 PM.


#19 aeajr

aeajr

    Voyager 1

  • *****
  • Posts: 13,673
  • Joined: 26 Jun 2015
  • Loc: Long Island, New York, USA

Posted 23 May 2020 - 02:04 PM

I don't expect the views of Jupiter is be magazine perfect. I know it won't be and yes I know Hubble has spoiled us all with the view it gives. But I was hoping that Jupiter would be a little bit bigger than this > O. I had the 8"XTi too but I never used the computerized finder.

Oh, that's a shame.  The Intelliscope is a fantastic tool for finding deep sky objects.   Easy to align and very accurate.  I loved mine.  But I have also learned other ways to locate targets.  LIke having a GPS in your car.  Punch in what you want to see and it shows you were to point the scope.

 

Of course, the Moon, Jupiter, Saturn, Venus and Mars are easy to find.  If that is all you care about than no need for star hopping, setting circles, GoTo, Intelliscope, StarSense or other hunting techniques.


Edited by aeajr, 23 May 2020 - 03:07 PM.


#20 Anony

Anony

    Mariner 2

  • -----
  • Posts: 298
  • Joined: 24 Oct 2018
  • Loc: Long Island, NY

Posted 23 May 2020 - 02:37 PM

 The planets were as I said. I saw Saturn and its rings. So tiny I could barely make it out. Mars was just a pinpoint of light, so was Venus. I was disappointed. Jupiter was just as I described it. Fuzzy ball of grey with two darker bands.

Hmm.... I'm a beginner myself, but in my 4" refractor I could clearly see Saturn's rings and bands on Jupiter.  Venus was certainly more than a point of light ... phases visible, and blaring. Too blaring actually. CA is a bit of an issue with Venus and Jupiter with that scope however.

 

With my 6" dob, on a poor seeing night, I was impressed with just how large Jupiter was. And that is also using cheapo MA eyepieces and I'm not 100% sure I even have this thing collimated correctly. Several bands were clearly visible. No red spot yet, but expect it's just not the time for that. As for Saturn, rings should be obvious. Looked pretty good to me. Saturn wasn't big, but it wasn't tiny either.

 

What magnifications were you using? For your 3x barlow, can you unscrew the lens and use it as a 1.5x barlow?


Edited by Anony, 23 May 2020 - 02:38 PM.

  • PatrickVt likes this

#21 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 23 May 2020 - 05:14 PM

Oh, that's a shame.  The Intelliscope is a fantastic tool for finding deep sky objects.   Easy to align and very accurate.  I loved mine.  But I have also learned other ways to locate targets.  LIke having a GPS in your car.  Punch in what you want to see and it shows you were to point the scope.

 

Of course, the Moon, Jupiter, Saturn, Venus and Mars are easy to find.  If that is all you care about than no need for star hopping, setting circles, GoTo, Intelliscope, StarSense or other hunting techniques.

I'm going to study DSO as well. I know the fall/winter sky fairly well. And I stay indoors during the spring/summer. Allergies and the fact that it's hard for me to breathe in the heat keeps me indoors. My favorite subject to study is the Orion nebula.I don't mind starhopping. It helps me to learn the sky.


  • aeajr likes this

#22 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 23 May 2020 - 05:21 PM

Hmm.... I'm a beginner myself, but in my 4" refractor I could clearly see Saturn's rings and bands on Jupiter.  Venus was certainly more than a point of light ... phases visible, and blaring. Too blaring actually. CA is a bit of an issue with Venus and Jupiter with that scope however.

 

With my 6" dob, on a poor seeing night, I was impressed with just how large Jupiter was. And that is also using cheapo MA eyepieces and I'm not 100% sure I even have this thing collimated correctly. Several bands were clearly visible. No red spot yet, but expect it's just not the time for that. As for Saturn, rings should be obvious. Looked pretty good to me. Saturn wasn't big, but it wasn't tiny either.

 

What magnifications were you using? For your 3x barlow, can you unscrew the lens and use it as a 1.5x barlow?

No, it doesn't come apart. I have some eyepieces at home, I'm currently at my daughter's in Evansville, In. for the summer. Watching my granddaughter til she goes back to school in the fall. I only saw two bands in my 8" dob.



#23 wavelandscott

wavelandscott

    Mariner 2

  • -----
  • Posts: 203
  • Joined: 23 Jan 2008
  • Loc: Ridgefield, Connecticut, USA

Posted 23 May 2020 - 07:33 PM

From my last experience with a dob, that would be a necessity. I got tired of standing pretty quick. Can you suggest one? I'm a pretty hefty gal at 223lbs. undecided.gif Yeah, okay so I like donuts and Starbucks.

I use a Stardust adjustable height chair.  I think they are a rebrand of a vestal chair (something like that)...

 

I too like donuts and my chair supports me well and without incident



#24 stargazer32864

stargazer32864

    Mariner 2

  • *****
  • topic starter
  • Posts: 217
  • Joined: 02 Jan 2006
  • Loc: Owensboro, KY

Posted 24 May 2020 - 12:46 AM

I use a Stardust adjustable height chair.  I think they are a rebrand of a vestal chair (something like that)...

 

I too like donuts and my chair supports me well and without incident

I looked for the Stardust website and couldn't find it,

 

Glazed donuts are my fav, they go good with coffee.



#25 Napp

Napp

    Vanguard

  • *****
  • Posts: 2,052
  • Joined: 26 Jul 2015
  • Loc: Florida, USA

Posted 24 May 2020 - 01:56 AM

Check out the Starbound chair.   I weigh about 225 lbs. and I love mine.  It’s stated capacity is 350 lbs.

Attached Thumbnails

  • 17EFE140-6415-4968-B5B1-F3BC1A928217.jpeg



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics