24 replies to this topic

[Thibaud]

Hi all,

So I finally got a chance to setup my Celestron 8" dob (1200mm FL) for the first time ever. It was also the first time ever I tried using a telescope in my entire life.

The whole setup process went well and I could even look at Mars with the 25mm EP. It was very small (48x if I understand how it works), but OK.

Based on this first experience, here are my basic questions:
- I could never have a super clean focus of the target. There was always some sort of rays of light « elongating » it as if it always had one « spike » coming out of it. I tried different ways / angles to look thru the EP but no difference. Could it come from the fact that Im wearing glasses ? Or does it sound more like a collimation issue ?
- It was fairly easy to get the target if my FOV with the 25mm EP, but impossible with the 7mm EP (I only have these two). What is the typical process ? Should I gradually go from 25 > 18 > 12 > 9 > 7mm and always try to keep the object in my FOV at each step ? Or is there another way to do it ?

Many thanks!

[daveb2022]

Did you try the 25 with the barlow?

[Neanderthal]

Hi all,

So I finally got a chance to setup my Celestron 8" dob (1200mm FL) for the first time ever. It was also the first time ever I tried using a telescope in my entire life.

The whole setup process went well and I could even look at Mars with the 25mm EP. It was very small (48x if I understand how it works), but OK.

Based on this first experience, here are my basic questions:
- I could never have a super clean focus of the target. There was always some sort of rays of light « elongating » it as if it always had one « spike » coming out of it. I tried different ways / angles to look thru the EP but no difference. Could it come from the fact that Im wearing glasses ? Or does it sound more like a collimation issue ?
- It was fairly easy to get the target if my FOV with the 25mm EP, but impossible with the 7mm EP (I only have these two). What is the typical process ? Should I gradually go from 25 > 18 > 12 > 9 > 7mm and always try to keep the object in my FOV at each step ? Or is there another way to do it ?

Many thanks!

Welcome to CN, great scope choice! 

I'll take a whack at your questions.

 

1. Mars would be very tiny in a 25mm EP. Mars is a very hard target to get a sharp image, even under good Seeing conditions. Some objects, like Jupiter, have been so bright that I see spikes (that's from the 4 vanes that support the Secondary mirror. Nothing wrong there, it's perfectly normal. Have you checked the collimation? A "tail" from a star is known as Coma.

 

2. Since Mars is so small, when you swapped from the 25mm to the 7mm, you decreased the FOV dramatically. A slight bump or move of the scope will take it off target. Practice your EP swaps on an easier (larger) target until you get the hang of it.

 

I'd suggest M42 - the Orion Nebula. It is very easy to find, and you can see it with just about any EP you can put in your Dob. Start with your 25mm and work your way through the higher magnifications as desired. Most importantly - have fun!

[aeajr]

Hi all,

So I finally got a chance to setup my Celestron 8" dob (1200mm FL) for the first time ever. It was also the first time ever I tried using a telescope in my entire life.

The whole setup process went well and I could even look at Mars with the 25mm EP. It was very small (48x if I understand how it works), but OK.

Based on this first experience, here are my basic questions:
- I could never have a super clean focus of the target. There was always some sort of rays of light « elongating » it as if it always had one « spike » coming out of it. I tried different ways / angles to look thru the EP but no difference. Could it come from the fact that Im wearing glasses ? Or does it sound more like a collimation issue ?
- It was fairly easy to get the target if my FOV with the 25mm EP, but impossible with the 7mm EP (I only have these two). What is the typical process ? Should I gradually go from 25 > 18 > 12 > 9 > 7mm and always try to keep the object in my FOV at each step ? Or is there another way to do it ?

Many thanks!

Congratulations on your new scope.  Is this a new scope or a used scope?  If new, could you post a link?  It always helps for us to know, with confidence, which scope you have. 

 

The only Dobs that Celestron sells today, that I know of, are the Starsense Explorer 8" and 10" Dobs.  Is that what you have?

https://www.celestro...onian-telescope

 

Your focus/spike problem - you don't say if it was one eyepiece or both.  

 

What is the light pollution like in your area.  I had a case where I thought I had found a comet.  What it turned out to be a reflection of my neighbor's house light off the eyepiece.   

 

I have astigmitism in my eyes.  If I take my glasses off, targets at low power can look spikey but it goes away as I get up over 100X.  

 

Transparency and seeing can greatly impact the image.

 

 

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

 

Transparency and Atmospheric Extinction
https://www.skyandte...ric-extinction/

 

 

Normally we move from the finder to the low power.  Once you have the target in the low power you can move up in power but the bigger the jump the harder it is to keep it in the field of view.

 

Assuming your eyepieces are Plossls, they have about a 50 degree AFOV.  So the 25 mm would have about a 1 degree field of view. While the 7 mm would have a field of view of about .29 degrees.  

 

Moving from one to the other while keeping the scope steady takes practice and is MUCH easier if you have smaller intermediate steps.  Say a 25 mm, 15 mm, 10 mm, 7 mm.

 

Here is an example of an eyepiece set showing the magnifications and jumps in a scope the same focal lenght as yours.  Note that zoom eyepieces give you a range of magnifications without having to change eyepieces.  I use zooms more than my single FL eyepieces.

 

 

AA SWA 70   38 mm            31.5 and 2.2 degrees  FOV   2”
Meade 82  20 mm               60X  and   1.37 degrees         2”  
    
ES 82          14 mm                86X and .95 degrees 
ES 82            11 mm            109X and .75 degrees
ES 82          8.8 mm             136X and .6 degrees      
ES 82          6.7 mm             179X and .45 degrees      
Meade 82   5.5 mm              218X and  37 degrees
ES 82           4.7 mm            255X and      .32 degrees
ES 82          8.8+2XB            272X and .3 degrees
ES 82          6.7+2XB            358X and .22 degrees
Meade 82   5.5+2XB           436X and .18 degrees

 

Baader Hyperion 8-24  zoom  50X to 150X
Baader Hyperion 8-24+1.5XB  75X to 225X (My most used 1.25” eyepiece)
Baader Hyperion 8-24+2XB   100X to 300X
Baader Hyperion 8-24+2.5XB 125X to 375X

 

 

It helps if you understand the language and math of eyepieces.

 

 

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/

 

Understanding and using a Barlow Lens
https://telescopicwa...ens-and-how-to/

[Thibaud]

Wow thanks a lot for your fast replies.

I didn’t realize Mars was considered a « hard » target, I will definitely follow your recommendation on M42 next time.

I also just realized there are « zoom EP », like this 8-24mm:
https://www.astrosho...m-1-25-/p,20224

Would it make sense to get one to help me getting familiar with the whole magnification process without adding the difficulty to swap hardware to it ? Or would you generally not recommend this type of « one size fits all » items ?

Thanks again!

[Neanderthal]

Mars in itself is very easy to find, I see it as a orange star with the naked eye.    It's just very small and no distinct delineation between the colors, a mix of orange, grayish-green and the white polar cap. Reminds me a sick fish, lol.

Edited by Neanderthal, 19 January 2023 - 04:19 PM.

[jimr2]

Thibaud,

 

As one person said above, using a zoom eyepiece does make it a lot easier--in my opinion--to change the power (and field of view) without having to manually switch out eyepieces, and thus losing the target and having to "find" it all over again. So I think the zooms do save some time and hassle, and most zooms now are of a fairly decent quality, approaching that of lower-medium-priced eyepieces, with the Baader zoom probably being one of the most highly regarded zoom (I don't have one of these so can't vouch for it for sure...). Celestron also has a zoom eyepiece if you wanted to stick with Celestron products.

 

Good luck with your "new" scope!

[Thibaud]

@aeajr, 

 

What a long reply, thank you. I'll try to answer to all your questions: 

 

I bought a Celestron 8" starsense brand new, here is the link: 

https://www.celestro...onian-telescope

 

The spike issue was only seen with the 25mm EP, since I couldn't even find Mars with the 7mm

 

Light pollution in my area is Bortle 5. Nasty streetlight not too far from my telescope. It didn't seem to be the issue but I will run a few tests to confirm.

 

My 25mm EP is a Celestron Omni Plössl (it came with the scope)

My 7mm EP is a Celestron X-Cel LX

My 2x Barlow is a Celestron X-Cel LX

 

I hope I answered your questions. I will also read all that you shared on EP and FOV. In the meantime, would you recommend a zoom 8-24mm to a beginner ?

 

Thank you.

[aeajr]

Wow thanks a lot for your fast replies.

I didn’t realize Mars was considered a « hard » target, I will definitely follow your recommendation on M42 next time.

I also just realized there are « zoom EP », like this 8-24mm:
https://www.astrosho...m-1-25-/p,20224

Would it make sense to get one to help me getting familiar with the whole magnification process without adding the difficulty to swap hardware to it ? Or would you generally not recommend this type of « one size fits all » items ?

Thanks again!

I have the Celestron zoom as well as the Baader Hyperion ( more expensive) and use them a LOT.  I use them more than my single FL eyepieces. 

 

So, yes, I would recommend getting that celestron zoom eyepiece.  It will also work well with your Barlow lens.  

Edited by aeajr, 19 January 2023 - 04:33 PM.

[Anony]

Wow thanks a lot for your fast replies.

I didn’t realize Mars was considered a « hard » target, I will definitely follow your recommendation on M42 next time.

I also just realized there are « zoom EP », like this 8-24mm:
https://www.astrosho...m-1-25-/p,20224

Would it make sense to get one to help me getting familiar with the whole magnification process without adding the difficulty to swap hardware to it ? Or would you generally not recommend this type of « one size fits all » items ?

Thanks again!

Mars is a pain. You may get some surface detail, but it's not an easy target.

 

If you have a barlow, I suggest trying that. If your barlow's bottom detaches, you can also do 1.5x by simply moving that section to your eyepiece.

 

But the Orion nebula (Pleiades as well) is where I'd suggest starting. Or Jupiter at least, not Mars.

 

And zooms can be great, but the Celestron at $158 + VAT? Ack.

In the US it's more like $70-$80ish, at least when on sale.  But I like zooms

personally ... it's more a preference thing, single eyepieces vs zooms.

Everyone is different there.

[Thibaud]

Thanks a lot for all your replies.

 

I think I have enough for my next run... once the clouds are gone.

 

I will keep you posted on the outcome (and will probably come back with more questions )

[drd715]

Learn how to check and adjust the columation on your dob. You might want to try an eyepiece around 12mm or so and in a design that produces a wider field of view. Not only does the wider field make it easier to locate your object of interest, it will keep the subject in the eyepiece view longer as it drifts across the view due to the earth's rotation.

Edited by drd715, 19 January 2023 - 04:37 PM.

[rgk901]

the flare could be your astigmatism or your scope isn't collimated / cooled properly.

At f/6 precision isn't as important as for a faster scope but the better you collimate it the betterthe views..

acclimating to temperature via waiting or fan is very important for high mag views.

to keep from losing the object when switching eyepieces, make sure the object is dead center before switching eyepieces.

If you have to refocus after switching because it's too blurry you can parfocalize your eyepieces easily using o-rings, such as below,then they will be much closer to focus and you won't lose your objects

https://www.amazon.c...ob_b_asin_title


a zoom is nice and well worth trying out... this will be a journey as tou develop your preferences

keep at it, read a lot and enjoy the scope!!

Edited by rgk901, 19 January 2023 - 04:40 PM.

[Paul Sweeney]

Hi Thibaud

The reason you could not get a clear image is the seeing. Right now we are having new cold fronts hitting every day. When the air is moving so fast, it is very turbulent. Trying to identify fine details is next to impossible under these conditions.

Normally, you should see 4 spikes around bright objects. One bright spike may be caused by an optical error, or by a smeared surface. The easiest way to find the problem is to rotate the optics. First identify in which direction the spike points. Now rotate the eyepiece. Did the spike rotate? If yes, it is coming from the eyepiece. If no, then try moving your head. If it moved, try taking off your glasses.... By a process of elimination you can find out where the spike is coming from. You can then report your findings here and we can help you find a solution.

When changing eyepieces, center the target first, then gently remove /insert the eyepiece. It takes a bit of practice to do it in the dark. If you adjust your finder very carefully, you can re-aquire the target by centering it in the finder.

The most inportant thing is just practicing. You can adjust the finder during the day, and practice eyepiece changes indoors at night. Let us know how you are progressing.

[vtornado]

I could never have a super clean focus of the target. There was always some sort of rays of light « elongating » it as if it always had one « spike » coming out of it.

 

This could be a lot of things.

First rotate the eyepiece.  Does the spike stay in the same place?  If it rotates with the

eyepiece, it could be oil from finger prints or eyebrows on the lens, or dew. 

 

Try taking off your glasses to eliminate that.  (You probably don't need them for Mars

unless your astigmatism is really bad.

 

Try the 18mm eyepiece.  Same spike?

 

I would say it could be diffraction spikes, but that should be symetrical.

Edited by vtornado, 19 January 2023 - 05:18 PM.

[nebula24x]

I'm a newb 2 years in with a z130 (5").
I've settled on using a 32mm (cell omni), celestron zoom 8-24, celestron 2x barlow and 5mm astrotech/starglider. Mostly planet watch so go to 5mm off the bat. Tried the svbony 6 and 9 but like the zoom and 5mm more (5mm seems fit best with my scope f9r max). Zoom is nice to find what you view most. Haven't tried new svbony 3-8 planetary but can see buying it. Though want to upgrade to 8" scope 1st.

[TheChosen]

Mars is one of the hardest targets I've experienced with my 8 inch DOB. If not in opposition, it is very small and extremely bright.. so the only thing I see with 10+mm eyepieces is glare.

 

25mm is way way too high. It will be a super bright blob with those spikes probably because of the too bright light playing tricks on the eyes like diffraction spikes.

Try centering Mars in your finder and then switching to the 7mm. It should be better. If you lose it in the eyepiece, just re-center in the finder. It is tricky, but doable.

 

Even better would be unscrewing the barlow and putting it on the 7mm.. That way you will achieve mags of about ~300x, which is ideal for Mars under perfect conditions. Otherwise, in normal conditions the 7mm alone should be OK.

 

To be honest the only way I saw some features on Mars was at about 300x and a variable polarizing filter to turn down the glare. 

 

Also , do not get your eyes dark adapted. Get a bright light around you so it doesn't blind you with the glare.

[Dave Mitsky]

If not in opposition, it is very small and extremely bright.. so the only thing I see with 10+mm eyepieces is glare.

I'm not sure what to make of this.  Mars varies in brightness from a maximum magnitude of −2.94 at the very closest opposition to a minimum of +1.86 when it is most distant from the Earth.  The latter figure is hardly extremely bright.

[KWB]

I'm not sure what to make of this.  Mars varies in brightness from a maximum magnitude of −2.94 at the very closest opposition to a minimum of +1.86 when it is most distant from the Earth.  The latter figure is hardly extremely bright.

[WillR]

I think you are off to a good start. Congrats on your new scope.

 

Have you tried the go to feature yet with your phone? That should get Mars in the FOV of your 7mm eyepiece. It will also have a data base of great targets.

 

Also be sure to  check out Jupiter while you can. Soon it will be gone from the evening sky until later in the summer.

 

As for zoom eyepieces, I have a Svbony 7-21 zoom. I use it mostly to split doubles. Lots of people swear by zoom eyepieces, and the Baader seems to be the one with the best reviews. 

[TheChosen]

I'm not sure what to make of this.  Mars varies in brightness from a maximum magnitude of −2.94 at the very closest opposition to a minimum of +1.86 when it is most distant from the Earth.  The latter figure is hardly extremely bright.

Last October , around 30th of October Mars was not in opposition yet. When viewed with an 8 inch DOB at low magnifications, the apparent brightness was very high while the size very small. My eyes could not see anything but glare. Had to increase magnification and add a variable polarizing filter to make out any features.

[joneb]

"cooled properly." ?

I had a 8" f6 Starhopper, from a 55 f deg. garage to 32 f deg. outside it would take about 30-45 minutes to acclimate. My 12.5" Dob w/a 2" thick mirror takes about 1-1.5 hours.

I

[Dave Mitsky]

Last October , around 30th of October Mars was not in opposition yet. When viewed with an 8 inch DOB at low magnifications, the apparent brightness was very high while the size very small. My eyes could not see anything but glare. Had to increase magnification and add a variable polarizing filter to make out any features.

Mars was less than 4 arc seconds in angular size then so it was hardly a good time to try to discern any surface features.  Its apparent magnitude was only +1.5.

 

How much magnification were you using before and after the increase in power?

[Philip Jodry]

For very bright things, I will reach for my 3 MM Zhumell.

[TheChosen]

Mars was less than 4 arc seconds in angular size then so it was hardly a good time to try to discern any surface features.  Its apparent magnitude was only +1.5.

 

How much magnification were you using before and after the increase in power?

Unfortunately my scope is at our summer house so the time I get to observe is very limited to the time we go there once in a month and even then I have a window of observation only from about 23:30 to 2:00 due to family obligations.

 

I started with about 80x magnification and increased to about 300x.