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Finder Scope Thoughts

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#1 GSqwid

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Posted 17 February 2019 - 11:12 PM

After years of playing with an old Meade 4.5" reflector I finally got my first "real" scope, an 8" SCT on an old but working CG5-GT mount.  I've been reading a lot but one issue I wasn't prepared for was how hard it was to see through the finder scope with my glasses!  The high eye relief lenses on the scope are fine, but the 6x30 finder scope has been causing me problems.  I can't get a good enough view of alignment stars to get them into the scope's field of view.

 

Any tips on workarounds or suggestions for a replacement/additional scope?  I've been reading about RACI, red dot, telrad, etc, but figured it made sense to get some expert input before experimenting.

 

Thanks you! 


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#2 Piet Le Roux

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Posted 17 February 2019 - 11:28 PM

After years of playing with an old Meade 4.5" reflector I finally got my first "real" scope, an 8" SCT on an old but working CG5-GT mount.  I've been reading a lot but one issue I wasn't prepared for was how hard it was to see through the finder scope with my glasses!  The high eye relief lenses on the scope are fine, but the 6x30 finder scope has been causing me problems.  I can't get a good enough view of alignment stars to get them into the scope's field of view.

 

Any tips on workarounds or suggestions for a replacement/additional scope?  I've been reading about RACI, red dot, telrad, etc, but figured it made sense to get some expert input before experimenting.

 

Thanks you! 

The most user friendly replacement for a finder scope that I have ever used was a green laser : Locally they have become very cheap and abundant.I build one in a 50mm tube and replaced my 50mm finder scope using the existing mount and adjusting screws. Now I can stand comfortably next to the scope and do a two star alignment without even bending!     


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#3 GSqwid

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Posted 17 February 2019 - 11:34 PM

The most user friendly replacement for a finder scope that I have ever used was a green laser : Locally they have become very cheap and abundant.I build one in a 50mm tube and replaced my 50mm finder scope using the existing mount and adjusting screws. Now I can stand comfortably next to the scope and do a two star alignment without even bending!     

I appreciate the thought, and they sound great, but due to the amount of air traffic in my area I'd be very hesitant to use a laser.



#4 TOMDEY

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Posted 18 February 2019 - 12:12 AM

If you look around at star parties... notice that most of the seasoned observers are taking their glasses on and off, depending on the circumstances. Have you tried your finder without glasses? Just changing the focus might make it fine for its intended purpose. I believe that many/most older observers (aka nearly all of us) go around wearing glasses, and take them off when at the eyepiece. As long as you don't have terrible astigmatism... that usually works!

 

PS: Some people are unaware that finders can indeed be focused. Sometimes, that involves moving the front lens (objective) by loosening that threaded retaining ring, rotating the lens cell to change focus, and then re-tightening the ring.   Tom

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#5 Stellar1

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Posted 18 February 2019 - 12:36 AM

Reticle finders in my opinion are the greatest thing since sliced bread, every scope I ever bought i'd remove the finder and use as door stop. If you can spring for it, the Baader Skysurfer V is awesome, you wont look back, Telrad is close second.



#6 GSqwid

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Posted 18 February 2019 - 12:46 AM

If you look around at star parties... notice that most of the seasoned observers are taking their glasses on and off, depending on the circumstances. Have you tried your finder without glasses? Just changing the focus might make it fine for its intended purpose. I believe that many/most older observers (aka nearly all of us) go around wearing glasses, and take them off when at the eyepiece. As long as you don't have terrible astigmatism... that usually works!

 

PS: Some people are unaware that finders can indeed be focused. Sometimes, that involves moving the front lens (objective) by loosening that threaded retaining ring, rotating the lens cell to change focus, and then re-tightening the ring.   Tom

 

Yeah... unfortunately I don't think going no glasses is an option for me. 

 

I will try adjusting the focus on the finder a bit.  It looks like the objective cell screws in and out on my scope, but whoever set it up hid the seam under a ring so I never noticed it.  your picture gave made me take a closer look.

 

That said, I don't think that focus is the issue.  I can see something big and bright (aka the moon) through it, though it kind of "drifts" in and out as a I try to adjust my view, but there is a sweet spot there somewhere.  Finding that spot with a star is much harder figure out the ideal position, and when kneeling and twisting at odd angles it just gets worse...

 

While I certainly love looking at the moon, I have greater aspirations for this scope.

 

Thanks again!



#7 GSqwid

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Posted 18 February 2019 - 12:49 AM

Reticle finders in my opinion are the greatest thing since sliced bread, every scope I ever bought i'd remove the finder and use as door stop. If you can spring for it, the Baader Skysurfer V is awesome, you wont look back, Telrad is close second.

 

I had been looking at the Telrad as an option.  Seems like it would at least get me close enough that I'd know what I want is in the finder scope, if not the telescope itself!  Between my glasses and a degree or two of error on my part, I'm not really sure what I'm looking at in the finder sometimes even when I seem to see something! 


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#8 Sky Muse

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Posted 18 February 2019 - 01:01 AM

The over-2000mm focal-length of an 8" Schmidt needs a "seeing-eye dog", or a seeing-eye owl, and in order to find anything when observing in a manual mode.  The next step up from a 6x30...

 

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

 

One of the first-page user-reviews states, "Eye relief is very comfortable...".  I don't know how true that is however.

 

It would need a bracket and base of course, and perhaps a bit of DIY along with that.  

 

Some have even used one of these for a finderscope, and the next step up from the 8x50...

 

https://www.bhphotov...ft=BI:514&smp=Y

 

With that one, a high-eye-relief eyepiece can be used with it.  Or, you could go with a Telrad or other red-dot finder...

 

https://agenaastro.c...1x-finders.html



#9 halx

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Posted 18 February 2019 - 01:08 AM

First of all, you should clarify your observing conditions. Is your sky bright or dark, can you tell what's the limiting magnitude you have to deal with naked-eye (wearing glasses)? Knowing your glasses power would also help in possible calculations.

 

At any rate, I believe that Telrad is an ultimate pointing solution as soon as you have a digital star chart capable of complete Telrad support. I don't use any other finders on my z12 dob for the past 10 years, even though always installing the optical one just for wide views. However, if you cannot see the Big Dipper's stars from your observing location even after good long dark adaptation Telrad will do no better than an ordinary red dot finder.



#10 sg6

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Posted 18 February 2019 - 02:40 AM

Any chance of a location for you?

When looking for bits like this it is often a good idea to locate a club and have a look at and if possible through a few finders. Also just see where and how they fit.

 

There are 4 or 5 different types, thought there were 5 but brain can only think of 4 - brain hasn't yet woken up. You are likely to find that one suits you and some you just do not get on with. I like a red dot and cannot get on with a telrad, there seems a greater number of people that are the other way round. Friend has no problem with a simple straight throiugh on his dobsonian, usually they are swapped out immediatly.



#11 pregulla

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Posted 18 February 2019 - 03:59 AM

I use a cheap red dot finder.  I am able to put an object within the view of 8mm eyepiece (0.4 degrees TFoV) with it. Magnifying finder is useful for starhopping to some targets, but I could live without it. 

 

There are also some finders that use regular eyepieces, so maybe you can use one of them with long ER eyepiece.



#12 Wouter1981

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Posted 18 February 2019 - 04:51 AM

A good finderscope is one of the best upgrades you can do on a telescope. My first telescope (114mm reflector with 0.956 inch eyepieces) had a 5x24 straight finderscope which was useless. Replacing it with a 9x50 RACI was a revelation and I was amazed how much I could see with the finderscope! I found myself looking more trough the finderscope and watching starfields than looking trough the telescope!

 

A laserpointer is what I use the most. It gets me close enough most of the time. You hesitation to use one because of the airtrafic is a good one, because even cheap ones can blind or at least distract a pilot over rather big distance. The reddot is almost as good as my laserpointer, but I live in a region with rather much lightpollution and often can't find a star visible close enough to my target. If your sky is darker, a reddot is a great thing. And lastly I use a 9x50 RACI to starhop when my green laser can't get me close enough. For me the green laser and 9x50 RACI is a perfect combination.

I've heard much good stuff about a Telrad but have never tried one.

 

So from my experience, buy a reddot and decent 9x50 RACI, like the one skywatcher sells, but they exist in lot of rebranded names.



#13 Jon Isaacs

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Posted 18 February 2019 - 06:40 AM

I had been looking at the Telrad as an option.  Seems like it would at least get me close enough that I'd know what I want is in the finder scope, if not the telescope itself!  Between my glasses and a degree or two of error on my part, I'm not really sure what I'm looking at in the finder sometimes even when I seem to see something! 

 

If your skies are dark, a Telrad is workable for most things and should be work reasonably well for GOTO alignment even with significant light pollution.  

 

But, I assume your 6x30 is a straight through finder.  My question:

 

Are you closing one eye when you use it?  If so, I suggest opening both eyes to start with.  When you do this, you will see the cross hairs from the finder with it's star field and superimposed on that is the naked eye star field and the alignment star will be very bright.   

 

You use the controller to move the alignment star towards the cross hairs.  When it pops into the field of view, it can be quite surprising because of it's brightness.  At that point, you close your other eye and center the alignment star in the finder.  

 

If the finder is aligned and you are using you lowest power, widest field eyepiece, the alignment star should be in the field of view.

 

The both eyes open method with a straight through finder has the advantage over a red dot or Telrad in that the straight through finder can be more precisely aligned because of the magnification and it has essentially zero parallax error.  It also has the advantage that you already own it.

 

The actual position needed to look through the finder can be awkward, you may want to adjust the tripod height and use a chair, an adjustable chair is best.

 

Jon



#14 Mike W.

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Posted 18 February 2019 - 08:10 AM

When I first tried my Red dot stock finder I had the issue of the dot completely covering the target star.

So I purchased and installed the Celestron up-grade right angle finder 9 X 50, it has finer cross hairs in the eyepiece than the stock single cross hair8 X 50 finder, that helped a lot, then I purchased a wide angle redicel eye piece for the scope so when I aligned the finder to the scope it was very easy to then point the scope at a target and that targe then in the scopes field of view.

 

You do understand that the scopes field of view is considerably less than that of the finder so having the two accurately aligned to each other is important.

 

If you could take a picture of your scope with the finder on it and post it, that will help us help you.

The type of mounting shoe and where it's mounted on your scope will also help us guide you.

 

Here is a link to an online store, this is the finder scope section,

 

https://agenaastro.c...der-scopes.html

 

Here's a link to our host's finder scope pages,

 

https://www.astronom...nderscopes.html


Edited by Mike W., 18 February 2019 - 08:15 AM.


#15 halx

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Posted 18 February 2019 - 11:23 AM

If you could take a picture of your scope with the finder on it and post it, that will help us help you.

That's for sure. The awkward mounting of the finder could contribute to the vignetting the OP experiencing with the short stock eye relief.

 

In addition, I should mention, that RACI finders considered not suitable for a GEM mount and a CAT combo. As most of them cannot be rotated in the rings (to accommodate the eyepiece for various RA positions) without re-alignment. A straight-through finder is more convenient on a GEM.


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#16 GSqwid

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Posted 18 February 2019 - 09:45 PM

Lots of great responses!  Thank you.  Multi-quote is a bit different than some forum software I use, so apologies if I missed anyone below!

 

At any rate, I believe that Telrad is an ultimate pointing solution as soon as you have a digital star chart capable of complete Telrad support. I don't use any other finders on my z12 dob for the past 10 years, even though always installing the optical one just for wide views. However, if you cannot see the Big Dipper's stars from your observing location even after good long dark adaptation Telrad will do no better than an ordinary red dot finder.

 

Suburban area.  Most of the stars used for alignment of the Celestron Goto are visible, so I'm thiking a Telrad or Red Dot would be workable for that, especially if used in conjunction with a solid finder scope.

 

Any chance of a location for you?

When looking for bits like this it is often a good idea to locate a club and have a look at and if possible through a few finders. Also just see where and how they fit.

 

There are 4 or 5 different types, thought there were 5 but brain can only think of 4 - brain hasn't yet woken up. You are likely to find that one suits you and some you just do not get on with. I like a red dot and cannot get on with a telrad, there seems a greater number of people that are the other way round. Friend has no problem with a simple straight throiugh on his dobsonian, usually they are swapped out immediatly.

 

Between Baltimore and DC, US East Coast.  There are a couple of clubs in the area, but most are taking a winter break at the moment.  Plus, though I'm sure plenty of folks would be more than willing to help, I want to try and at least get the set up and alignment done on my own before taking my scope to a star party.  

 

 

I use a cheap red dot finder.  I am able to put an object within the view of 8mm eyepiece (0.4 degrees TFoV) with it. Magnifying finder is useful for starhopping to some targets, but I could live without it. 

 

There are also some finders that use regular eyepieces, so maybe you can use one of them with long ER eyepiece.

 

I've seen some folks using small (50 to 80mm) refactors with short focal lengths as finders.  It seems like it might be overkill for my purposes, but using a "comfortable" eyepiece would be nice.  Astrophotography interests me and that seems like such a refractor would be a good option for an entry-level guide scope, but I'm still trying to find alignment stars so that is a ways off.

 

 

If your skies are dark, a Telrad is workable for most things and should be work reasonably well for GOTO alignment even with significant light pollution.  

 

But, I assume your 6x30 is a straight through finder.  My question:

 

Are you closing one eye when you use it?  If so, I suggest opening both eyes to start with.  When you do this, you will see the cross hairs from the finder with it's star field and superimposed on that is the naked eye star field and the alignment star will be very bright.   

 

You use the controller to move the alignment star towards the cross hairs.  When it pops into the field of view, it can be quite surprising because of it's brightness.  At that point, you close your other eye and center the alignment star in the finder.  

 

If the finder is aligned and you are using you lowest power, widest field eyepiece, the alignment star should be in the field of view.

 

The both eyes open method with a straight through finder has the advantage over a red dot or Telrad in that the straight through finder can be more precisely aligned because of the magnification and it has essentially zero parallax error.  It also has the advantage that you already own it.

 

The actual position needed to look through the finder can be awkward, you may want to adjust the tripod height and use a chair, an adjustable chair is best.

 

Jon

Thanks for the tips.  I had been closing one eye, but I'll try applying your suggestions!

 

When I first tried my Red dot stock finder I had the issue of the dot completely covering the target star.

So I purchased and installed the Celestron up-grade right angle finder 9 X 50, it has finer cross hairs in the eyepiece than the stock single cross hair8 X 50 finder, that helped a lot, then I purchased a wide angle redicel eye piece for the scope so when I aligned the finder to the scope it was very easy to then point the scope at a target and that targe then in the scopes field of view.

 

You do understand that the scopes field of view is considerably less than that of the finder so having the two accurately aligned to each other is important.

 

If you could take a picture of your scope with the finder on it and post it, that will help us help you.

The type of mounting shoe and where it's mounted on your scope will also help us guide you.

 

Here is a link to an online store, this is the finder scope section,

 

https://agenaastro.c...der-scopes.html

 

Here's a link to our host's finder scope pages,

 

https://www.astronom...nderscopes.html

Finder is well aligned, though I'll admit it might have a bit of parallax error.  It seemed to be good finding the moon and the one star I managed to see through it!

 

That's for sure. The awkward mounting of the finder could contribute to the vignetting the OP experiencing with the short stock eye relief.

 

In addition, I should mention, that RACI finders considered not suitable for a GEM mount and a CAT combo. As most of them cannot be rotated in the rings (to accommodate the eyepiece for various RA positions) without re-alignment. A straight-through finder is more convenient on a GEM.

Thanks for the tip on RACI.  I had not thought of that, but it makes perfect sense!

 

And a couple pictures of my set up below.  Thanks again!

 

F2
F3
F1


#17 Jond105

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Posted 18 February 2019 - 10:02 PM

Seeing this now, I think the straight through works for you. Like Jon said, and something I just found out in December myself, the straight through with both eyes open looking at the sky work beautifully for me with my refractors on my GEM, not so much on the dob, but give keeping both eyes open a try and see how that works out for you before any upgrades. If anything maybe a straight through 9x50 at that point. Just my opinion on everything.

#18 gnowellsct

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Posted 18 February 2019 - 10:20 PM

Ditch the 6x30.  If you want to remain with straight through, which is my preferred finder, get a 7 x 50 or 8 x 50 illuminated finder with rear focus.

 

For your glasses:  you can leave them on, but polycarbonate glasses will scratch.  For astronomy I have glasses-made-of-glass, which one shouldn't have to specify, but there it is.  

 

A Takahashi finder is expensive but primo, has the illumination and rear focus, and the optics are good enough that it becomes virtually a second (or in my case a third) telescope.  

 

Take the finder to a gun store (! I don't have anything to do with guns, but I got to them for the caps) and get a BUTLER CREEK spring loaded lens cap.   This will help you keep the finder dew free when not in use.  

 

Vixen finders are very good.

 

Among the budget finders I like the Meade which has rear focus, no illumination, but the optic is decent and the cross hairs are heavy black so you can see them even when it's dark out and you have no illumination.

 

Greg N



#19 gnowellsct

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Posted 18 February 2019 - 10:25 PM

the last celestron 9x50 I got with the thin extended eyepiece barrel I put in the trash along with the finder bracket.  Some things are too awful to sell.



#20 GSqwid

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Posted 19 February 2019 - 12:08 AM

Seeing this now, I think the straight through works for you. Like Jon said, and something I just found out in December myself, the straight through with both eyes open looking at the sky work beautifully for me with my refractors on my GEM, not so much on the dob, but give keeping both eyes open a try and see how that works out for you before any upgrades. If anything maybe a straight through 9x50 at that point. Just my opinion on everything.

Sounds like plan A.  Hopefully the weather will give me a chance to try this out soon!

 

Ditch the 6x30.  If you want to remain with straight through, which is my preferred finder, get a 7 x 50 or 8 x 50 illuminated finder with rear focus.

 

For your glasses:  you can leave them on, but polycarbonate glasses will scratch.  For astronomy I have glasses-made-of-glass, which one shouldn't have to specify, but there it is.  

 

A Takahashi finder is expensive but primo, has the illumination and rear focus, and the optics are good enough that it becomes virtually a second (or in my case a third) telescope.  

 

Take the finder to a gun store (! I don't have anything to do with guns, but I got to them for the caps) and get a BUTLER CREEK spring loaded lens cap.   This will help you keep the finder dew free when not in use.  

 

Vixen finders are very good.

 

Among the budget finders I like the Meade which has rear focus, no illumination, but the optic is decent and the cross hairs are heavy black so you can see them even when it's dark out and you have no illumination.

 

Greg N

Takahashi looks great, but the price tag would be approaching what I paid for the OTA and mount! 

 

The Meade certainly would be an option, though I'm also thinking a less expensive red dot or Telrad might make sense until I'm ready to invest in a really nice finder that can eventually double as a guide scope!  It is interesting that low-end refractors are in the same price range as a the large straight-through finders.  I guess once you add in the cost of an eyepiece with a reticle and the beefier mounting hardware the price ends up being more.

 

Speaking of hardware, what mounting hardware would I need?  I search for Celestron brackets but keep coming up with dovetails for the OTA.  A few options seem to include mounts that match the screws on my scope, but not all of them.

 

Thanks again for all the help!



#21 Mike W.

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Posted 19 February 2019 - 08:16 AM

This one will bolt right on where yours is now and use the same screws.

 

It will do for now, guide scopes come along every once in a while.

 

https://www.cloudyni...-for-edge-11hd/



#22 Mike W.

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Posted 19 February 2019 - 08:38 AM

https://www.highpoin...iwAGdAOr1eHf47E

 

This one from Highpoint is another bolt right on, it has a thumb screw to secure the back section, just loosen the screw and rotate the eyepiece where you want it without losing alignment.


Edited by Mike W., 19 February 2019 - 08:40 AM.


#23 GSqwid

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Posted 19 February 2019 - 09:06 PM

Thanks again for the suggestions!

 

Sounds like trying a couple more times with the existing straight through makes sense. 

 

That said, considering it is a GoTo mount, would I gain much getting a Telrad versus a cheap red dot if I wanted to try a no magnification option?  I can see the value of the Telrad for orienting on dimmer objects by aligning the rings with brighter ones, but I'm not sure I would need that ability at this time.  Any thoughts?



#24 Mike W.

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Posted 19 February 2019 - 10:07 PM

Telrad's have a pretty strong following, and there are Astro charts that use the Telrads redicel pattern to mark faint targets. 

It's better than the red dot that comes with the Celestron,, dimming control is better plus the Telrad's battiers are "AA" much cheaper than the button battery that powers the red dot.


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#25 halx

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Posted 20 February 2019 - 03:37 AM

That said, considering it is a GoTo mount, would I gain much getting a Telrad versus a cheap red dot if I wanted to try a no magnification option?  I can see the value of the Telrad for orienting on dimmer objects by aligning the rings with brighter ones, but I'm not sure I would need that ability at this time.  Any thoughts?

GoTo mounts are hard to navigate manually (even by button-slewing) with the necessary accuracy anyway due to the limited directions of motion freedom provided. Then, Telrad is less efficient on an EQ mount as slots in its rings will be rotating relative to the Horizon (just made a note for myself, that the App could actually help with that too). So I believe that at the moment you would align faster by just centering a GoTo Model Adjustment Star using the RDF first, then a wide EP with an illuminated cross/or dot (or with the optical finder instead), then press "Align" and GoTo target objects in the vicinity from the database (not 100% sure your controller allows that, but most scope control apps can compensate to some extent).

 

I agree with Mike on the above, Telrad might be still a better RDF due to its characteristics dedicated to the task (better brightness control up to the possibility of modding the circuit, better collimation, repeatability, reliability, etc). Add to that the fact that its center is not obstructed by some red blob, thus much fainter stars are centerable when necessary.

 

By the way, an RDF could help to work with the RACI finder if you decided on it later, as its sole purpose will be to fine-tune the centering as with the wide EP (you may never find a wide enough crosshair EP for the C8 focal range so an optical finder might be still a viable step for the C8 alignment), the straight-through pointing phase is still beneficial though, an RDF/Telrad could serve that purpose perfectly.

Some more on the RACI. It's not that a big deal now that its EP position might be awkward on a GEM, as having a rough (first stage RDF) pointer will require just a brief look through that EP for the alignment star plausible centering, as we can double-check and adjust even more accurately with the main EP, that's nothing like the typical tedious star hopping with the finder.

 

Just thoughts.


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