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2nd scope advise

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#1 MP173

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Posted 12 June 2019 - 03:22 PM

My current scope is an ETX90RA which I use with the 3 trilegs - tabletop.  Love the scope but understand the limitations.

 

Thinking seriously about a second scope.  The email ads from Astronomics for their AT102ED has triggered this as a possible options.  

 

Pros:

F7 - 714 focal length will give a wide FOV.

Portable

 

Cons:

Will need to purchase a tripod...another $200.

Will not provide high power which I use for double stars.  My 12mm will provide 60x.  

 

Astronomics, when I explained my current scope, suggested the ETX125 indicating the extra 35mm of aperature will provide an increase over the 90mm (and the 102mm of AT102ED). 

 

Price for the AT102Ed is $599 plus tripod cost.

Price for the ETX125 is$629, including tripod.

 

My observations are done in my backyard in a fairly light polluted area (northwest Indiana) with limiting mag of about 4.3.  

 

I enjoy the ETX90RA but realize limitations (primarily on galaxies, clusters, etc).  It is also narrow FOV which isnt really a factor.  I understand the FOV for the ETX125 will be narrower but will have higher power. 

 

Primarily I use my scope for doubles and open clusters.

 

Comments on the two scopes and a discussion on what the differences are would be appreciated.

 

Ed

 



#2 Sam M

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Posted 12 June 2019 - 03:50 PM

Just sayin'...

https://www.highpoin...n-telescope-ad8


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#3 havasman

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Posted 12 June 2019 - 04:02 PM

You will also need a mount for the very capable AT102ED and maybe a finder. But it would make an excellent package. Higher mag is easily available via short focal length eyepieces. A 4.7mm ep yields 152x and a bright 0.7mm exit pupil. Magnification > 200x is available with the exit pupil still at 0.5mm.

 

The clear aperture w/o refraction from mechanics in the optical path will make those magnifications cleaner and brighter than you will get via ETX. I had 3 ETX's some years ago and did not favor them at all for their comparatively dull images.

 

Many of us are very enthusiastic about the widefield capabilities of an f7 refractor. That should change your observing more than anything else.


Edited by havasman, 12 June 2019 - 04:13 PM.

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#4 MP173

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Posted 12 June 2019 - 04:49 PM

Thanks for the replies so far.  I have given thought to a dob.

 

How critical would it be to have a finderscope on the F7 scope?  My star hopping skills are pretty good, but a bright object is required to start.

 

Ed


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#5 aeajr

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Posted 12 June 2019 - 05:42 PM

Sounds like your budget is around $800.

 

So, what can you do with $800 and how will it fit into your life and your observing goals.

 

The Dob - Will size and weight be a factor?  Dobs have the best bang for the buck.  A 6" Dob is fairly portable at about 35 pounds.  it offers wider views and higher mag opportunities due to the greater aperture than the 90.  A Skywatcher 6" has a 2" focuser so you can get pretty wide.   This is the entry to the transition from grab and to to light bucket. Can be either.  

 

Or you can easily get an 8" PushTo Dob or 10" manual Dob for that and could stretch to a 12" without much effort.  This would be a HUGE aperture upgrade with a reasonable balance of wide and high power.  8" is about 45 pounds, 10" about 60 and 12" about 85 pounds, but they can be moved in two pieces.  Do you have a way to store and move a larger scope?  

 

 

Computer - you are considering an ETX 125.  Nice scope with full Goto features and almost double the aperture of the ETX 90.  Nice upgrade, compact in size but not wide field.  Do you want wide field?   If you do, this is not the scope for you, but a great scope for planets, doubles and most DSOs under .8 degree in span.   BTW, the majority of DSOs are under .8 degree in span, but not all. 

 

 

If you are looking at GoTo, what about a Celestron NexStar 6E SCT?  150 mm aperture, full GoTo, still fairly light and compact.  Wider FOV and more aperture than the ETX 125 and you can put a Focal Reducer on it to get a wider FOV though I am not sure how wide this will take you.  Others will have to complement.  One downside on this scope is that it can not be used manually.  You can't just release the clutches as it doesn't have clutches. So you have to use the hand control to move it.

 

If you want to go to an 8" SCT you get into the $1200 range. 

 

 

AT102ED - I presume this is an APO refractor.  Very nice!  Probably comparable in aperture effect to the ETX 125 because there is no central obstruction.  I would call them equal.   Manual or computerized depending on what mount you use.   Will provide a wider FOV than your ETX 90.   Far more portable than an 8" Dob but nowhere near the aperture. 

 

 

So, where are your priorities?   

  • Do you plan to replace the ETX 90 or complement it?
  • How portable do you need the new scope to be?  
  • Does it have to go in your car?  What will fit?
  • Do you want a manual mount, PushTo, or full GoTo?

 

These are the questions I feel you need to answer first.  Then you can go shopping and see what you can get for your $800.

 

I look at the optics pool as:

  • binoculars
  • grab and go
  • light bucket

I presume you have binoculars

 

Your ETX 90 is grab and go.

 

Are you looking for a bigger grab and go or is it time for the light bucket?

 

Inquiring minds want to know. 


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#6 NYJohn S

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Posted 12 June 2019 - 05:44 PM

Ed, I just use a red dot on my AT102ED to get to the starting point. After that I use my ES 68º 24mm and hop through the eyepiece. I love the AT102ED and the new one with the sliding dew shield will be even better for travel. I just keep thinking you may want some more aperture since you have a 90mm scope. The wide-field views are very nice though with the AT102ED so it will be a different experience compared to what you have now with the ETX90.


Edited by NYJohn S, 13 June 2019 - 10:56 AM.

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#7 csa/montana

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Posted 12 June 2019 - 05:56 PM

Moving to Equipment, as there are multiple types of telescopes being discussed.  


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#8 aeajr

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Posted 12 June 2019 - 05:59 PM

Thanks for the replies so far.  I have given thought to a dob.

 

How critical would it be to have a finderscope on the F7 scope?  My star hopping skills are pretty good, but a bright object is required to start.

 

Ed

I feel a finder is required on anything above 400 mm FL and frankly I want a finder on that too.  A RDF is enough if you have a wide view low power eyepiece.  If you are star hopping, a Telrad is better but I don't own one.   

 

I like the combo of a RDF and a RACI on my 8" and 12" Dobs.  On my other scopes I use mostly RDF.  No reason to have a scope without some kind of finder.


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#9 MP173

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Posted 12 June 2019 - 07:22 PM

Thanks for the replies so far.

 

A little more background....

 

Double stars have become my favorite objects, probably due to the limitations of the scope and my observing area.  I do not travel from my backyard.  Perhaps I will in the future, but not now.  The ETX90RA is a great grab and go and I will always keep this scope unless it is retired due to mechanical issues.  This scope works the doubles pretty well.  I have difficulty with splitting unequal pairs below 3", but that is ok as there are literally hundreds, if not thousands of doubles out there. 

 

My second favorite DSO to view are open clusters.  A typical observing session will mix doubles with open clusters in the same area.  Globulars and galaxies are challenges - usually just a "puff of smoke" with no detail unless it is an M13 type.  Even M31 shows no detail.  It is realized that to achieve that detail that it is necessary to power up along with aperature.  

 

I dont need "go to" capability.  The star hopping aspect is enjoyed and is considered part of the enjoyment.  Is it safe to assume with the ETX125 the "go to" can be turned off and the scope can be used as an alt -atz scope?  I have very little knowledge about scopes other than the ETX90RA.  I had a 60mm Sears refractor as a child and purchased a 60mm refractor at a garage sale a couple of years ago.  The sharp views in the garage sale scope were stunning, but the 4mm EP made locating anything but the moon very difficult.  The EP is .965mm diameter.  

 

The goal here is not to chase aperature, but simply to offer an alternative to the 90mm ETX.  I would prefer "quality of view" over "quantity" of objects.  

 

How much obstruction does the ETX125 have and how does that impact the view?   Again, realize that I have nothing to base the views on other than my ETX90Ra.  Perhaps I should go to a star party and view other scopes.

 

Also, my eyepiece collection are Meade Plossls....can these be used effectively with the AT102?

 

Thanks for the help.

 

Ed


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#10 aeajr

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Posted 12 June 2019 - 07:53 PM

Plossls are good eyepieces in any scope.

Etx125 is a Goto by design. It can limp as a manual scope but you won't like it. I have an ETX125. So, that one is out.

Based on your comments I would say the AT102 is an excellent choice. You will get more aperture gain than the number would suggest due to the aperture obstruction in the ETX90 MAK design. But I think those GCs and galaxies will still be gray fuzzies.

A 6" Dob would bring some of those brighter GC and bright nebula into play. I think you will need 8"+ to really change things based on my experience in a dark white zone with ETX80, ETX125, 8" and 12" Dob scopes.

Go for it!
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#11 havasman

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Posted 12 June 2019 - 09:50 PM

Perhaps I should go to a star party and view other scopes.   waytogo.gif

 

Also, my eyepiece collection are Meade Plossls....can these be used effectively with the AT102?   Sure. There are better but they'll certainly work.

 

Thanks for the help.

 

Ed



#12 aeajr

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Posted 12 June 2019 - 10:19 PM

Ed,

 

You mentioned Plossls.  I remembered I had this:

 

Plossls are very good eyepieces  – Good discussion -
https://www.cloudyni...s/#entry8285208



#13 Jond105

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Posted 12 June 2019 - 10:42 PM

Yeah I mean, seeing one of these 102ED’s up close and personal, and knowing the new ones have a retractable dew shield, I can’t see you being disappointed with one of these scopes. Especially on the clusters like you also like viewing.

#14 jgraham

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Posted 13 June 2019 - 03:10 AM

+1

 

The biggest problem here is that there are so many good choices, and the 102ED is a nice scope.

 

For me, this thread checks a lot of boxes. I have this same ETX-90, complete with the tabletop legs, an Orion 100ED, and an ETX-125PE and I enjoy deepsky and double star observing (plus others). The ETX-90 is a great little scope, the biggest problem that I had with mine is that I'd run out of light before I ran out of magnification; the light grasp of the 90mm was the limiting factor. To fix that I bought my ETX-125 as a visual companion to my imaging gear, and in that role is has performed beautifully. The 125 is a big step up from the little 90 and inherits a lot of the attractive characteristics of the 90 including sharp, high contrast images and a compact design that is very comfortable to use. I bought my 100ED as a slightly larger companion to my original Celestron 80ED. Both are wonderful scopes and refractors have many nice characteristics of there own such as being able to max-out the exit pupil (low power) without worrying about seeing the shadow of the secondary (because they don't have one). The one issue that I have with refractors (and I have several up to a 6" f/8 achro) is that they can be a bit cumbersome to use. You need to mount them high to be able to sit comfortably beneath them and they are so long that the eyepiece swings through quite a height change as it moves around the sky. A nice observing chair like the Starbound helps a lot. In contrast, my ETX-125 is so compact that I can easily snuggle up to the scope and in altaz mode (where I use it most of the time) it is very comfortable to use. Also, modern UWA eyepieces go a long way to improving the field of view of long focal length scopes like the 125 while at the same time offering good magnification. For star-hopping, I like a nice RACI finder and I configure all of my scopes to accept one. I recently added a Vixen style finder mount to my 125 which makes it a wonderful star-hopping scope for those time when I want to go off-road. It is soooo nice being able to switch back'n forth between GoTo and star-hopping, using the handbox to slew the scope.

 

Soooo, if'n it were me I'd certainly take a look at the 102ED if I wanted to try something different that was a nice step up from the little ETX-90. However, the ETX-125 is also worth considering. It will be a much larger version of what you are already used to and makes for a very compact system that is very comfortable to use. The wider aperture will also offer the best resolution for double star work. As far as light grasp, since the 102ED doesn't have a central obstruction or reflective optics it will compare well with the ETX-125 and it will perform much better for wide field work. As far as comfort I'd give the edge to the 125.

 

Lot's of excellent options! Have fun shopping around!

 

Just for yucks, my baby with its shiny new RACI finder...

 

ETX-125PE (5-23-2019)-1.jpg

 

 


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#15 carolinaskies

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Posted 13 June 2019 - 11:17 AM

OK, you've given some very definite parameters... 

- Double star observing
- Open Cluster observing
- Static light polluted observing site
- Star hopping to targets 
- Have ETX90

The ETX90/125 central obstruction is around 31% of the center. Effective aperture is closer to about (-10%) vs clear aperture refractor so 81mm/113mm.  It's not a 31% subtraction of light gathering like some think.   The 102mm gains your about 25% more light gathering area (102 vs 81) and about 10% less (102 vs 113).   Neither is an exceptional change (gainging 35% by moving to the ETX125)  in viewing either double stars or clusters whether open or globular. 

There is a telescope though that is inexpensive but much better for your requirements.  The XT6 is a 6" F/8 Newtonian.  It has the same field of view of the ETX90, but has a resolution of .76" vs the ETXs 1.29/.93 and the 102's 1.14.    This means you have better double seperation, and considerably more light grasp to make the star clusters pop out.   Beyond the 6" any larger and the current crop of offerings are more wide-field telescopes in the F/4-F/5 range.  If you were to buy an Alt-Az mount like the following link you can star hop and have easy access to fine controls.  https://www.highpoin...tripod-maz01-00

 



#16 jgraham

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Posted 13 June 2019 - 01:02 PM

+1

Dobs remain the value champion. :)
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#17 rkelley8493

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Posted 13 June 2019 - 01:05 PM

Thanks for the replies so far.

 

A little more background....

 

Double stars have become my favorite objects, probably due to the limitations of the scope and my observing area.  I do not travel from my backyard.  Perhaps I will in the future, but not now.  The ETX90RA is a great grab and go and I will always keep this scope unless it is retired due to mechanical issues.  This scope works the doubles pretty well.  I have difficulty with splitting unequal pairs below 3", but that is ok as there are literally hundreds, if not thousands of doubles out there. 

 

My second favorite DSO to view are open clusters.  A typical observing session will mix doubles with open clusters in the same area.  Globulars and galaxies are challenges - usually just a "puff of smoke" with no detail unless it is an M13 type.  Even M31 shows no detail.  It is realized that to achieve that detail that it is necessary to power up along with aperature.  

 

I dont need "go to" capability.  The star hopping aspect is enjoyed and is considered part of the enjoyment.  Is it safe to assume with the ETX125 the "go to" can be turned off and the scope can be used as an alt -atz scope?  I have very little knowledge about scopes other than the ETX90RA.  I had a 60mm Sears refractor as a child and purchased a 60mm refractor at a garage sale a couple of years ago.  The sharp views in the garage sale scope were stunning, but the 4mm EP made locating anything but the moon very difficult.  The EP is .965mm diameter.  

 

The goal here is not to chase aperature, but simply to offer an alternative to the 90mm ETX.  I would prefer "quality of view" over "quantity" of objects.  

 

How much obstruction does the ETX125 have and how does that impact the view?   Again, realize that I have nothing to base the views on other than my ETX90Ra.  Perhaps I should go to a star party and view other scopes.

 

Also, my eyepiece collection are Meade Plossls....can these be used effectively with the AT102?

 

Thanks for the help.

 

Ed

M31 will only show detail if you are under dark skies and/or have a large aperture. My 10" Dob shows M31 as a bright gray oval from my light polluted town. From a dark site, you can see the dust lanes much more clearly.

Very wise of you not to chase aperture or get the "aperture fever". I would recommend going with the Astro-Tech refractor as it would be a better alternative to your 90mm ETX. The ETX125 would almost be redundant, and you probably wouldn't use the 90 near as much or at all on down the road. The refractor doesn't have a central obstruction, so technically it's greater than or equal to the 125mm Mak-Cass. The refractor will also have much better sharpness & contrast, so those faint gray galaxy clouds will show up much easier against a jet black sky background. 

Since you also mentioned open clusters, the AT102ED would be much better suited for those. Viewing the Pleiades with an f/7 refractor is like a religious experience. The narrow field of view of a Mak really limits it to high power viewing, i.e. lunar/planetary and double stars. Having a wider field scope would compliment what you currently have much better.


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#18 jgraham

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Posted 13 June 2019 - 02:13 PM

Ugh, I played the aperture fever game for 30 years as an active amateur telescope maker eventually topping out with my homebuilt 16.5" f/6.5 Newtonian (the green monster in my Avatar). Big scopes are a lot of fun, but they don't improve the view as much as you'd think. For me, it has been far more valuable to be comfortable at the eyepiece with a nice seat and to take the time to relax and see what there is to see in a given field. My 16 year journey into modern imaging (on top of over 30 years of film) has also taught me what to look for. It has been soooo helpful having access to my own, unprocessed source images as these accurately show exactly what an object looks like and exactly where it is before the image has been processed beyond all recognition. Sooo, while I do enjoy my biggo scopes, my smaller scopes get used far more often and why I emphasize comfort over aperture. Bigger scopes are nice, but they come with an ever increasing pain in the rumpus factor. The best scope in the world is the one that you actually use the most, and that sweet spot is a very personal place. For me, that tends to be in the 3.5" - 8" range.



#19 havasman

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Posted 13 June 2019 - 04:51 PM

Thanks for the replies so far.  I have given thought to a dob.

 

How critical would it be to have a finderscope on the F7 scope?  My star hopping skills are pretty good, but a bright object is required to start.

 

Ed

An rdf IS a finder and it's what I use on my AT115EDT. Works great.


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#20 Jond105

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Posted 13 June 2019 - 05:00 PM

Yeah, I agree with havasman an RDF would work fine. I prefer a straight through with refractors, but that’s personal opinion.

#21 NYJohn S

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Posted 13 June 2019 - 05:11 PM

Thanks for the replies so far.

 

A little more background....

 

Double stars have become my favorite objects, probably due to the limitations of the scope and my observing area.  I do not travel from my backyard.  Perhaps I will in the future, but not now.  The ETX90RA is a great grab and go and I will always keep this scope unless it is retired due to mechanical issues.  This scope works the doubles pretty well.  I have difficulty with splitting unequal pairs below 3", but that is ok as there are literally hundreds, if not thousands of doubles out there. 

 

My second favorite DSO to view are open clusters.  A typical observing session will mix doubles with open clusters in the same area.  Globulars and galaxies are challenges - usually just a "puff of smoke" with no detail unless it is an M13 type.  Even M31 shows no detail.  It is realized that to achieve that detail that it is necessary to power up along with aperature.  

 

I dont need "go to" capability.  The star hopping aspect is enjoyed and is considered part of the enjoyment.  Is it safe to assume with the ETX125 the "go to" can be turned off and the scope can be used as an alt -atz scope?  I have very little knowledge about scopes other than the ETX90RA.  I had a 60mm Sears refractor as a child and purchased a 60mm refractor at a garage sale a couple of years ago.  The sharp views in the garage sale scope were stunning, but the 4mm EP made locating anything but the moon very difficult.  The EP is .965mm diameter.  

 

The goal here is not to chase aperature, but simply to offer an alternative to the 90mm ETX.  I would prefer "quality of view" over "quantity" of objects.  

 

How much obstruction does the ETX125 have and how does that impact the view?   Again, realize that I have nothing to base the views on other than my ETX90Ra.  Perhaps I should go to a star party and view other scopes.

 

Also, my eyepiece collection are Meade Plossls....can these be used effectively with the AT102?

 

Thanks for the help.

 

Ed

I think you answered your own question here Ed.

 

I honestly thought maybe you should go for a larger aperture scope like an 8" dob but if you're not trying to chase down faint dso then I think the AT102ED will be a good choice. The refractor views will be something different for you compared to the ETX 90 or 125. They just have those sharp, crisp, pinpoint stars and that contrast you don't get with a scope with a central obstruction. It sounds like you saw that with the 60mm refractor. Plus you'll have the ability to go wide when viewing some of the larger objects. At my last dark site trip I was using magnifications as low as 18x for M24 and as high as 260x for Jupiter. I think for a 4" scope the AT102ED does a lot of things well and is a very versatile instrument. Just make sure it's mounted well for high power work since you like splitting doubles. 


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#22 MP173

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Posted 13 June 2019 - 05:40 PM

Thanks for all the advise.

 

The discussion on the central obstruction is something that I never realized.  Makes a lot of sense.

 

RKelly....thanks for the description on viewing Pleidies....I am looking for quality.  

 

I had the opportunity once to view thru a 14" scope at a university and was stunned at how dull the stars appeared.  Perhaps it was the conditions, but I recall thinking to myself that my little ETX, while not grabbing nearly the light had very sharp images.

 

Keep the comments and suggestions coming...

 

Ed


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#23 Jon Isaacs

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Posted 14 June 2019 - 07:27 AM

I feel a finder is required on anything above 400 mm FL and frankly I want a finder on that too.  A RDF is enough if you have a wide view low power eyepiece.  If you are star hopping, a Telrad is better but I don't own one.   

 

I like the combo of a RDF and a RACI on my 8" and 12" Dobs.  On my other scopes I use mostly RDF.  No reason to have a scope without some kind of finder.

 

Personally I have red dot type finders on my refractors but rarely use them, I can point them intuitively to the right spot.  I do use 2 inch eyepieces so the 714mm focal length of the AT-102ED can provide as much as a 3.7 degree TFoV, a magnifying finder is unnecessary.  

 

Ed (the OP) is star hopping with a ETX-90, that has a maximum field of view of 1.25 degrees so he's already very good at star hopping.  

 

As far as the AT-102ED goes, it's a very good scope for splitting doubles, definitely better than a 4 inch Mak and on unequal doubles, better than a 5 inch Mak.  

 

As far as the dull stars in the 14 inch.  Something doesn't seem right.  Maybe it was at high magnifications or the scope wasn't stable.  The first thing I notice when using a large aperture scope is just how many stars there are and how bright they are.  A 14 inch goes 3.0 magnitudes deeper than a 90mm.  That means that Polaris in the 14 inch will be slightly brighter than Rigel in the 90mm.  Stars are bright.  

 

Personally, I like my 10 inch Dob for doubles.  But the seeing here is generally quite good and I have all the tools and eyepieces and understand how to get the most out of a Dob, both optically and mechanically.  Dobs are as good as it gets when it comes to star hopping.  An 8 inch Dob would have a wider field of view than your ETX-90 and be more potent for deep sky. 

 

How much obstruction does the ETX125 have and how does that impact the view?   Again, realize that I have nothing to base the views on other than my ETX90Ra.  Perhaps I should go to a star party and view other scopes.

 

 

 

The ETX-90 and the ETX-125 are very similar when it comes to the central obstruction.  I cannot find the data on the currrent ETX-125 but the original version had a 40% CO.  When comparing a Mak to a refractor, one has to consider not only the central obstruction but the reflectivity losses of the mirrors etc.  Very good coatings like the Celestron Starbright XLT transmit about 84% of the light so combined with the secondary obstruction, about 70% of the light entering the scope reaches the eyepiece.  This is in comparison to a refractor.  

 

There are a lot of good choices.  I suspect that your current favorite objects are the result of the fact that these are the objects best suited for a 90mm Mak.  Another scope that offers a wider field of view, captures more light, will likely allow you to appreciate a wider range of objects. 

 

Jon


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#24 MP173

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Posted 14 June 2019 - 07:30 AM

Jon:

You are correct.  I have gravitated to doubles due to the limitations (strengths) of the ETX.  

 

I am leaning toward the refractor. 

 

Ed


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#25 aeajr

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Posted 14 June 2019 - 08:57 AM

Knowing what I know today, if I were to wipe the slate clean I would have:

 

  • Binoculars - 8X40, 10X50 and maybe 20X80 on a mount
  • 100 mm ED refractor on a solid mount, probably a GoTo mount with clutches.  Maybe even a (I can't believe I am saying this) a Goto EQ mount.  
  • 12" Dob

That would be it!  Three tools.  and they would all live in the garage or a shed, ground level, so they were super easy to deploy and use. 

 

I have 6 scopes today and each has a job. Three of them were free to me, not planned purchases.   But if I were to move and had to leave it all behind, that is the set I would build at the new location. 

 

And I would probably add something that I could loan out to friends, maybe an 80 mm manual refractor or a tabletop reflector.

 

Ed, I don't know if that is of any help to you.

 

If you could handle it I would definitely encourage you to go to an 8" Dob or larger.   But the 102 ED refractor seems to be the right choice for you at this time based on your current goals and situation. 

 

The ETX 90 will probably gather dust after you get that. They are too close and too similar in task for you to need both so you will default to the refractor most of the time.   


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