53 replies to this topic

[Nightskyman]

I’ve had my dob for two months now, the weather hasn’t be cooperative most of the time but I have had some good nights and look forward to the journey ahead. I’ve discussed some of my questions in part on other threads but I thought I would summarize my final remaining questions all in one thread. I have a few basic eyepieces, but I really would like and intend to add and upgrade to something better without breaking the bank. I have narrowed my choices to the following. Celestron X-cel LX, AT Paradigm Dual ED ( or Agena Starguider Dual ED), and the AT UWAs. I also currently have an Orion high power 2x 4 element Barlow. I wear eyeglasses and have a moderate astigmatism so eye relief is a consideration. Other than getting an optical finder scope ( likely a RACI), to replace the red dot which is impossible to use with its location on my scope. There is no available space to move it to because of the phone cradle on the top of the tube for the StarSense, Otherwise, I am all set to go! As far as choosing sizes, if I understand correctly, after factoring the focal length of the scope, I choose pieces based on the magnification that I want and the AFOV that I prefer. Wow, that was a mouthful, but it summarizes the only concerns or questions that I have at this point. Sorry for being so windy and hope the long post isn’t bad etiquette.

[Barlowbill]

Hello  Being "windy" is definitely not bad etiquette here on CN.  I have a handful of Paradigm eyepieces and the work just fine.  Their field of view isn't huge but they are better than a Plossl. You can't go wrong with a RACI.  I use one which sits next to a green laser pointer in a dual mount from Orion.  I wouldn't have it any other way.  Stay steady at it.  Sounds like you have a pretty good gripe on it.

[Nightskyman]

Barlowbill, How do you feel about a 6x30 vs a 8x 50?

[sevenofnine]

+1 on Bill's post. Most here will agree that an 8x50 RACI is the better choice. However, hidden in Bill's answer is another option...a green laser finder. Since you are using StarSense as a finder, a laser might be all you need to get the scope in the right general area before you engage StarSense. Like anything in this hobby, there are pros and cons. Certainly, safety is one of them. They are not for use around airports but rural areas are fine IMO. The laser can be tuned to a high degree of precision. So much so that I rarely use any other kind of finder. Good luck! 

 

https://agenaastro.c...vixen-foot.html.

https://agenaastro.c...er-pointer.html.

[Barlowbill]

Mine is a 9X50.  I like the power of a 9.  However, it has been pointed out to me (my a member who knows far more than I ever will) that an 8 has a larger field of view.  I don't remember how much larger.  I doubt it is much,

[aeajr]

When I discuss upgrades I always ask about goals and what problem you are trying to address.

Finder. What is the problem? You have Starsense Explorer on your Dob. Why do you need a finder? How will you use it?

[rocco13]

Hello  Being "windy" is definitely not bad etiquette here on CN.  I have a handful of Paradigm eyepieces and the work just fine.  Their field of view isn't huge but they are better than a Plossl. You can't go wrong with a RACI.  I use one which sits next to a green laser pointer in a dual mount from Orion.  I wouldn't have it any other way.  Stay steady at it.  Sounds like you have a pretty good gripe on it.

^ Ditto what he said. I love my Starguider(Paradigm) EP, especially for the price point. My most-used EP.

 

And the RACI really made finding stuff from star charts as easy as can be. Even though I read engineer's plans for a living and can read them upside down, reversed, and every other orientation, but something about NOT having to do that with start charts in the dark makes things so much more enjoyable.

Edited by rocco13, 27 January 2023 - 09:01 AM.

[vtornado]

I have had several xcel-x and i have almost the full line of paradigm eyepieces.

They are close to having the same performance.  So much so that

the telescope they are in and the eyes in your head may make the difference.

 

I had one of the shorter xcel-x 7??? and the Paradidm 8 was sharper for lunar/planetary.

 

I had both the 25 xcel and the 25 paradigm and the 25 xcel was slightly better off axis

at f/5.  However the paradigm was slightly wider.

 

You have star sense, so finder use should be limited?   Does the red dot hurt your

neck/back?  If you want the optical finder for ergonomics, I would get the 6x30.

It is lighter to avoid balance problems and has a wider field of view.  the 50mm

finders will show more stars.

 

As far as glasses use,  depending upon the amount of astigmatism, it only becomes

annoying at certain exit pupils.   ( eyepiece_focal_len / f_ratio).  My astimatism is

around 1 diopter.  It starts becoming apparent at 4mm exit pupil.  For stuff like

lunar and planetary where a 1mm exit pupil is used, it is not notices.  A refractive

error can be accounted for with the focuser.

 

I frequently find my glasses as dirty and scratched, which I don't notice in the

daytime.  Also a fair amount of stray light leaks in through the side.

I prefer to view with glasses off.  Unless as I say I am using low power and

large exit pupils

[NeroStar]

I'll second the RACI recommendation.  I have three of the Celestron 9 X 50 RACIs and they've all been good.  The Celestron LX 12mm works well with my 12' Meade Dob, and the 15mm eye relief is adequate with eyeglasses on..  I can't imagine your experience with that EP would be much different.  I prefer a wider field of view, but it's not too bad.  

[Nightskyman]

aeajr, eyepieces, not so much a problem just would like better quality eyepieces to enjoy better views but with budget in mind. Finderscope, yes the red dot finder forces you to make unbelievable contortions to use it. StarSense is nice, BUT, there is something about my nature that as I become more experienced, I want to have the ability and enjoy the experience of finding my way around the sky by my own efforts!

[Nightskyman]

a tornado, my astigmatism is 1.25 diopter in one eye and 1.75 diopter in the other, just a moderate astigmatism.

[Nightskyman]

I read about how certain eye pieces work better in certain type scopes but I don’t understand that concept or how to figure which is which. Exit pupil, I know what it is but don’t understand how it works in relationship to viewing. Is shorter or longer better? What effect does it have on viewing? I they’re a certain number, such as 7mm that you don’t want to go past? 

[Nightskyman]

Is there a way to “guesstimate” which finderscope (6x30 or 8x50) would work or cause a balance issue short of trying each and returning one on them ?

[aeajr]

Is there a way to “guesstimate” which finderscope (6x30 or 8x50) would work or cause a balance issue short of trying each and returning one on them ?

I understand your desire to learn how to find things without the Starsense Explorer feature.  I had an XT8 Intelliscope. The PushTo was great but I wanted to learn other techniques.  I played with star hopping but in my very light polluted area I found it quite frustrating.  I have whole sections of the sky with no stars.

 

I learned how to use AltAz coordinates and that works great.  My Apertura AD12 is set up for AltAz coordinates and that is now my main method with all of my scopes.  But I would LOVE to add StarSense Explorer to it.  Perhaps I will some day. 

 

Most 8" Dobs will carry an 8X50 or 9X50 just fine.  I had a 9X50 on my Orion XT8i.  Balance was fine, but you can easily offset any balance issue by adding a small amount of weight down by the mirror.  I use these magnets.

https://www.harborfr...nets-97504.html

 

 A pair weight about 3.5 oz.  I have 7 pairs, each pair wrapped in duct tape so they don't mark the tube.  I move them up and down the tube for balance as I go from heavy eyepieces to lighter ones.  When I added my Telrad, 3 pairs went down by the mirror and live them all the time, to offset the weight of the Telrad.   I now have a 12" Apertura AD12 and use the same method.  It has an 8X50 and the Telrad.

 

I don't know what kind of shoe is on the RDF you have.  If it is a standard shoe, you can slip the RDF out and slip in the 8X50.

 

I have this one.  Mine is labeled Apertura, but it is the same finder.  It came with my scope.  On the XT8i I had a similar Orion 9X50.

https://agenaastro.c...age-finder.html

Edited by aeajr, 27 January 2023 - 11:43 AM.

[Neanderthal]

.....I have narrowed my choices to the following. Celestron X-cel LX, AT Paradigm Dual ED ( or Agena Starguider Dual ED), and the AT UWAs. I also currently have an Orion high power 2x 4 element Barlow. I wear eyeglasses and have a moderate astigmatism so eye relief is a consideration....

 

If you are going to observe with your eyeglasses on, I'd go for the AT UWA's, and def if you don't wear them! None of these choices are ideal for eyeglass wearers, but at least with the UWA's will still have more FOV after losing some of it due to your eyeglasses. The UWA's are absolutely worth the difference in cost amongst this group you've selected.

[aeajr]

I read about how certain eye pieces work better in certain type scopes but I don’t understand that concept or how to figure which is which. Exit pupil, I know what it is but don’t understand how it works in relationship to viewing. Is shorter or longer better? What effect does it have on viewing? I they’re a certain number, such as 7mm that you don’t want to go past? 

As described in the article I posted, low focal ratio scopes, say F7 and lower,  deliver the outer light beams to the eyepiece at a steeper angle than scopes of higher focal ratio.   This means that the eyepiece has to turn those light rays more in order to get a uniformly even image across the field of view.

 

A cheaper, less well corrected eyepiece, will show more edge distortion than better corrected eyepieces.  How much varies greatly.  Without actual testing the only way to know how much is to read the reports here or to buy them and try them.

 

Some people are very bothered by this edge distortion.  Others are less bothered.

 

Most of my single FL eyepieces are Explore Scientific 82 series. These are very well corrected and performed well in my F5.9 (same as yours) XT8i and in my F5 AD12.  There is some distortion along the outer 5% or so of the field but I can't say I notice it or that it bothers me at all.  Others might make a big fuss over that, but I don't care.  Looks good to me.

 

My 2" 38 mm 70 degree low power wide view Agena Astro Super Wide Angle (same as the Orion Q70 series)  is a lower cost eyepiece that is not as well corrected as the ES 82s.  There is more edge distortion but, again, it doesn't bother me in the slightest.  I have been using this for years and have no plans to replace it.

 

This distortion, based on the focal ratio of the scope, tends to grow as the apparent field of view gets wider.   Plossls, about 50 degree AFOV, look good in just about anything.  As they get wider, 60, 70, 80, 90, 100+ degrees AFOV, it is harder for the eyepiece designer to correct that edge issue so the really good ones are very expensive.

 

From what I read, the Astro Tech SWS 82 degree eyepieces do a pretty good job with this.  I don't have one so I can't give you a direct comparison to my ES 82s, but I would say they would probably be a very good choice for you to build your eyepiece set around if you are trying to get the best bang for the buck.

 

Here is my eyepiece set as it would be in my XT8i, now sold.  As it is the same FL as yours you would get similar results.   Note that my most used eyepiece is the Baader Hyperion 8-24 zoom.  The bolded ones are the ones I used the most. 

 

Orion XT8i – 8”/203 mm manual Dob Newtonian, 1200 mm FL F5.9
Resolving power -  .6 arc Seconds

 

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

[aeajr]

a tornado, my astigmatism is 1.25 diopter in one eye and 1.75 diopter in the other, just a moderate astigmatism.

Glasses are a tricky topic.  Eye relief is the key issue.   Depending on your glasses you may be fine with 16 mm of eye relief or you may need 20 mm.   I can't say what the minimum you will need will be.

 

Eye relief is defined as how close or far from the eyepiece lens you eye has to be in order for you to see the full field of view presented by the eyepiece. Your glasses may pervent you from getting close enough to the lens to see the full field of view of an eyepiece that has only 12 mm of eye relief.   You might need 16 mm or 18 mm or even 20 mm.

 

Take a look at the eyepieces you are using today.  What are their eye relief specifications?  When you are wearing your glasses, can you see the full field of view?  Can you see to the edge of the field where the field stop defines the edge of the view.

 

Most, but maybe not all eyepieces longer than 18 mm will have enough eye relief to be used with your glasses.  When you get shorter than that, some eyepieces will not have enough eye relief for your needs.  

 

For example, the Astro Tech 18 mm SWA has 16 mm of eye relief.   That might be fine for you or it might not be enough for you to see the full field of view with your glasses on.

 

The Astro Tech 13 mm SWA only has 12 mm of eye relief.  Very likely that won't be enough with your glasses.

 

The AT Paradigm 18 mm has 18 mm of eye relief - likely to be enough with your glasses

 

The AT Paradigm 15 mm has 12 mm of eye relief - likely not enough.

 

Your options

 

Only buy eyepieces that have the necessary eye relief to accomodate your glasses.  It is usually the shorter focal lengths where you have to be careful.

 

Or

 

Stay with longer focal lenght eyepieces and use a Barlow lens (2X, 2.5X or 3X) to simulate the shorter eyepieces to achieve higher powers

 

Or

 

Use your glasses with the longer focal length eyepieces and take them off for the shorter focal lenght eyepieces.

 

These are your options when it comes to acomodating your glasses.

[EsaT]

I wear eyeglasses and have a moderate astigmatism so eye relief is a consideration.

At high magnifications/small exit pupil you might get away without glasses, because only center part of lens of your eye is in use.

But for most uses better to count in use of glasses.

Eye relief should be around 20mm for that.

 

Exit pupil is eyepiece focal length / telescope focal ratio or telescope aperture / magnification.
Something like 1mm exit pupil would be small.

Depending on your age max usable exit pupil without light going to waste is like 7 to 6mm.

(with age max size of eye's pupil decreases)

 

Barlowbill, How do you feel about a 6x30 vs a 8x 50?

6x30 is low end and not really fit for 8" telescope:

50mm aperture collects ~180% more light helping to find deep sky objects.

[CarolinaBanker]

Why would you add a RACI to a StarSense dob? It makes zero sense, the whole point of paying the premium is to get StarSense. You have had the scope for two months, the weakest link in the optical chain is going to be the observer, not the EP. I think that more observing time would add far more to your capabilities than a new EP. I’d also suggest reading about what you’re looking at, in other threads you asked for lists of objects which in my mind means it’s likely fruitful to learn what’s in the sky and make observing it richer. You may want to consider sketching as well.

[edify]

What ever you decide, don't break the bank. I would also advice to go as wide view as you can on the low power eyepieces and even on that end you really could do with one. Have fun enjoying every bit of time you can when looking at the black sky.

[Second Time Around]

I agree there's no need to add a RACI to a Starsense Explorer scope - or indeed any sort of finder. This is because Starsense Explorer itself is the finder.

 

In fact, unless you live somewhere with a lot of light pollution, you may not even need the red dot finder.  Just point your scope in the general direction of a bright star and you'll probably see it on your phone screen. A planet, or better still the moon, will make it even easier. Then just line the crosshair up on the object and Starsense Explorer will do the rest.

 

Because of not needing to buy a finder, the extra cost of a Starsense Explorer scope is not as much as it first appears. 

 

Plus you have the benefit of another scope as well.  I've just given mine away minus the bracket literally today to a  keen young couple who can't afford much.

 

Many of us have bought the least expensive Starsense Explorer scope and adapted the bracket to fit any standard Synta finder shoe.  A search here on Cloudy Nights will show lots of ways to do so.

 

This means that you can use Starsense Explorer on all your scopes, and none of them actually needs a RACI.

 

Of course you may decide you'd like one anyway.  I use a 40mm RACI on my 72mm ED.  However, it's not used as a finder but a wide angle scope for night vision.

 

Plus, as you said, you like the idea of finding your own objects by starhopping.  I fully get this - there's the thrill of the chase and a sense of achievement when you succeed.  Indeed, I still sometimes starhop just for the fun of it myself.

 

So I'd suggest buying another finder at this stage isn't a priority.  Instead, I'd use the saving in cost to buy other accessories first.

[Nightskyman]

CarolinaBanker, please reread my post, I want to eventually learn and be able to find my own way around the sky. Reread Second Time Around’s post as well, he gets it when he said “I fully get this - there's the thrill of the chase and a sense of achievement when you succeed”. This will make me strong, not a weak link as you put it. The StarSense will be used to assist me in getting started and will likely be great for my grandson to use down the road. As fat as having it two months, that has nothing to do with it. As far as asking questions of people’s opinions in other threads, I just look for others experienced opinions and will use them to “formulate my own pathway”. After all, isn’t that the point of a beginners forum? 

[Nightskyman]

aeajr, thanks for all the input. My sky is a Bortle 6-7 and it can sometimes be a challenge. A RACI makes sense to me as it can serve several purposes, not just a finder scope to align objects. Do you find that to be true for you? I have a lower end Barlow, a Orion high power 2x 4 element. When used to give a higher magnification, does the view suffer much in your opinion? I like the idea of a series that is parafocal but maybe I should consider mixing or adding where needed. For what’s worth, the StarSense technology works nicely, but not flawlessly.

[Nightskyman]

I realize that it is mostly just a term, and I understand what it means, how it applies, and how it is calculated, but Is a f/5.9 considered fast or slow as it seems to me to fall in the middle? 

[Barlowbill]

Kinda in the middle.  Look, if you want a RACI, get a RACI.  I have a 9X50 and love it.  A 7mm exit pupil is allegedly about the max for young folks.  I'm not a young folk.  My Optometrist claims I have about a 7mm,  I don't believe him.  Doesn't matter.  Don't get hung up on exit pupil.  If an eyepiece produces a little more than your eye can handle (your personal exit pupil), so what.  You "waste" a little light.  Big deal.  With a Newtonian, if you waste too much you may begin to show a shadow caused by the secondary mirror.  Not good.  It means you should not have purchased that 40mm eyepiece (or whatever).  A little bit won't hurt.  I have a handful of Barlows (Duh!).  Don't worry about them.  The one you have will suffice.

I certainly don't worry about parfocal eyepieces.  Tweaking focus doesn't bother me.  It doesn't require much.  My recommendation is to purchase at least around 70 degree eyepieces.  I don't have any!  Wish I did.  The only exception is, I love my Baader Hyperion zoom.  It is a keeper.  Back to the finder scope.  I would NOT get a 6X30.  If you took my 9X50 I guess I could live with an 8X50.  I wouldn't like it.  Weight is not an issue.  As aeajr said, cheap magnets can solve such problems.

One more piece of advice: You don't need a bunch of eyepieces.  One decent wide sweeper (preferably a 2") and one or two high magnification (5mm and 8mm) and a couple or so mid-range.  Or a zoom (8-24, or some such).  Stay steady at it.  Peace