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#1 Dave Bush

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Posted 16 September 2019 - 12:39 AM

A couple questions.  

 

The off-white color, it is essentially the same as the Celestron EdgeHD off-white?  Sure looks like it.

 

GSO focuser, has any one attached one?  Is it a direct fit?

 

Thanks.



#2 Redbetter

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Posted 16 September 2019 - 02:05 AM

I haven't used the branded GSO focuser.  I have used the $69 two speed 2" that Lunt sells that from all appearances is a the GSO without any badging.  The only difference I am aware of is that it is only tapped for a single compression ring hole.  I remedied that by tapping a second hole.  Added a finder shoe for an RDF to it.  I used a bit of tape to shim the focuser flange as it is just a little narrower than the 80 f/5 OTA.  3 layers of simple Scotch tape worked from what I recall.

 

Keep in mind that when you add the extra heft of a 2" diagonal and max field 2" eyepiece, the assembly becomes much heavier and the balance point shifts to under the focuser.  The little dovetail is insufficient for this, so plan on rings or some other sort of upgrade.  The little dovetail is both too far forward and has no nuts on the two bolts/screws that attach it.  Instead they are threaded into the tubewall.  When I briefly tested this with a 2" diagonal and eyepiece I did not like the sounds that emanated from the attachment points, so I ordered rings.  I either added a longer dovetail or already had one on hand to allow me to attach to the mount further to the rear for balance. 



#3 Old Man

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Posted 16 September 2019 - 02:39 AM

  I have the GSO branded focuser and it fit like a glove. But, you will need a longer dovetail, so I got rings and dovetail from Orion. Also used the Scopestuff 2" quartz 99% mirror diagonal as Agena was out of stock on the GSO diagonal.

  It really opens up the view, I know I have spent way too much on the upgrades, but it was well worth it IMO. Mine puts out fantastic widefield views and will take high power extremely well.

  I added a picatinny rail on top of the rings along with a 1" riser with a 45 degree side to it, have my Pinty GLP mounted on top and a Pinty red/green dot finder on the 45 degree side, works terrific. I absolutely love mine and even with spending way more than the scope costs, I believe it was worth it. Mine is a keeper.

 

           Mike


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#4 dwmedic

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Posted 16 September 2019 - 10:17 AM

 Mine wasn't really what I would call an off white, more of a light tan or khaki.



#5 Agatha

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Posted 16 September 2019 - 03:28 PM

As mentioned, it is more like khaki color.   This picture will help show difference from white.

 

image.jpeg


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#6 Dave Bush

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Posted 16 September 2019 - 03:30 PM

Thanks Linda.  Well, it can always be painted.  


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#7 Dave Bush

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Posted 16 September 2019 - 03:35 PM

I haven't used the branded GSO focuser.  I have used the $69 two speed 2" that Lunt sells that from all appearances is a the GSO without any badging.  The only difference I am aware of is that it is only tapped for a single compression ring hole.  I remedied that by tapping a second hole.  Added a finder shoe for an RDF to it.  I used a bit of tape to shim the focuser flange as it is just a little narrower than the 80 f/5 OTA.  3 layers of simple Scotch tape worked from what I recall.

 

Keep in mind that when you add the extra heft of a 2" diagonal and max field 2" eyepiece, the assembly becomes much heavier and the balance point shifts to under the focuser.  The little dovetail is insufficient for this, so plan on rings or some other sort of upgrade.  The little dovetail is both too far forward and has no nuts on the two bolts/screws that attach it.  Instead they are threaded into the tubewall.  When I briefly tested this with a 2" diagonal and eyepiece I did not like the sounds that emanated from the attachment points, so I ordered rings.  I either added a longer dovetail or already had one on hand to allow me to attach to the mount further to the rear for balance. 

I plan on mounting it on the top of my EdgeHD 8 (Evolution mount).  I want to keep weight to a minimum so rings and such would be too much and look less sleek.  I would likely re-attach the dovetail using screws and nuts.

But then again, I may just keep the original focuser.  I'm not likely to want or need to use 2" eyepieces in it.  I would be using it to provide a wider field (>1.5º) than I could get through the main scope.



#8 corax

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Posted 16 September 2019 - 04:14 PM

I recently did the conversion, also using the Lunt 2" focuser:

 

https://luntsolarsys...cuser-3-travel/

 

I had an old Celestron 2" SCT diagonal I converted for refractor use with a cheap 2" nosepiece. It's piggybacked on my C8 using ScopeStuff rings and rail. The whole assembly is VERY heavy, and pushes the limits of my AVX mount.

 

I really enjoy the piggyback aspect, though. I think it pretty much requires adjustable rings for the 80mm in order to look at the same target through both scopes.

 

I kinda like the ivory color.


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#9 Redbetter

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Posted 16 September 2019 - 04:54 PM

I plan on mounting it on the top of my EdgeHD 8 (Evolution mount).  I want to keep weight to a minimum so rings and such would be too much and look less sleek.  I would likely re-attach the dovetail using screws and nuts.

But then again, I may just keep the original focuser.  I'm not likely to want or need to use 2" eyepieces in it.  I would be using it to provide a wider field (>1.5º) than I could get through the main scope.

The extra weight of the focuser is not that much.  It is the combination of the extra mass of the diagonal and particularly a heavy 2" eyepiece that make it problematic for balance and structural support by the little dovetail.  One could add the focuser providing flexibility and still use 1.25" diagonal and eyepieces, yet always have the option to go to 2" later. 



#10 Dave Bush

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Posted 16 September 2019 - 05:04 PM

 

I really enjoy the piggyback aspect, though. I think it pretty much requires adjustable rings for the 80mm in order to look at the same target through both scopes.

 

I hadn't thought about that.  



#11 Redbetter

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Posted 16 September 2019 - 05:20 PM

BTW, from what I recall, the baffle face was pressed against the front screw/bolt of the dovetail on mine.  So you might have to move the baffle back a little to have room for a nut.   Although there is some thickness to the baffle (since it has folds along the tubewall), there should still be space for nuts if it is repositioned.   I wanted better field illumination so I moved the baffle back to the place where the rear screw used to be.



#12 corax

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Posted 16 September 2019 - 11:34 PM

Mine actually came with nuts for the dovetail bolts, but when I removed the dovetail I replaced the bolts with shorter (~7mm) cap screws, and added some small nylon washers. The thread size is M4. I didn't have any trouble threading the nuts with both the focuser and the lens cell removed.



#13 tony_spina

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Posted 16 September 2019 - 11:41 PM

A couple questions.  

 

The off-white color, it is essentially the same as the Celestron EdgeHD off-white?  Sure looks like it.

 

GSO focuser, has any one attached one?  Is it a direct fit?

 

Thanks.

Yes it’s a direct fit. Takes less the 5min to install



#14 Redbetter

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Posted 17 September 2019 - 01:54 AM

Mine actually came with nuts for the dovetail bolts, but when I removed the dovetail I replaced the bolts with shorter (~7mm) cap screws, and added some small nylon washers. The thread size is M4. I didn't have any trouble threading the nuts with both the focuser and the lens cell removed.

 

Are you saying the new bolts you used are M4?  Because the ones on mine are M5-0.8.



#15 corax

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Posted 17 September 2019 - 08:13 AM

Are you saying the new bolts you used are M4?  Because the ones on mine are M5-0.8.

No, the stock bolts and nuts were. Sounds like some manufacturing variability. Maybe they figured they could get away without nuts if the used slightly larger bolts?

 

I bought the scope 2 years ago -- added the new focuser and piggybacked it this year.


Edited by corax, 17 September 2019 - 08:22 AM.


#16 Old Man

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Posted 18 September 2019 - 04:31 AM

   If I remember right, my stock dovetail also had nuts on the inside. Like you say, probably just some variability in manufacturing. Here is a pic of mine mounted on my AVX. You can see the GLP and the multi retical red/green dot mounted on the 45 degree side of the riser which is also completely removable, it is fixed with quick release levers which are on the other side in the pic.

   Like I said, way too much in upgrades, but it puts out such great views I will never part with it, I don't know if it is me or the scope, but for an achro, I don't notice any CA in mine at all. I have looked for it and maybe my brain doesn't process that, I don't know. I know it should suffer from it, but I don't see it, and I have been visual since I started in 1996, so I do know what CA looks like. But this one is a keeper.

20190917_13.JPG


Edited by Old Man, 18 September 2019 - 04:43 AM.

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#17 corax

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Posted 18 September 2019 - 02:51 PM

I don't notice any CA in mine at all.

I don't either. Nor spherical aberration. I know they've got to be there, but for whatever reason they just don't bother me.



#18 Jim1804

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Posted 18 September 2019 - 10:26 PM

attachicon.gif 20190917_13.JPG   If I remember right, my stock dovetail also had nuts on the inside. Like you say, probably just some variability in manufacturing. Here is a pic of mine mounted on my AVX. You can see the GLP and the multi retical red/green dot mounted on the 45 degree side of the riser which is also completely removable, it is fixed with quick release levers which are on the other side in the pic.

   Like I said, way too much in upgrades, but it puts out such great views I will never part with it, I don't know if it is me or the scope, but for an achro, I don't notice any CA in mine at all. I have looked for it and maybe my brain doesn't process that, I don't know. I know it should suffer from it, but I don't see it, and I have been visual since I started in 1996, so I do know what CA looks like. But this one is a keeper.

attachicon.gif 20190917_13.JPG

Your ST80 AdventureScope looks like it's been assimilated by the Borg bow.gif . Awesome setup!

 

BTW, the only time I notice CA is on Venus - nice big purple halo. But for Milky Way scanning, no problem. As someone said on another thread, put the lens cap on with only the center cap off, and you've got a 40mm APO like view of Venus and the moon...



#19 Redbetter

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Posted 18 September 2019 - 11:19 PM

I don't know how people can't see the obvious color blur on short achros.  To me this demonstrates that people's color sensitivity varies far more than the optics themselves.  The calculated color blur of an 80 f/5 achro is ~6.3 times the airy disk diameter.  There is nothing subtle about it.   The Violet halo is readily apparent at a substantial diameter on Jupiter even at 67x.  By comparison an 80 f/11.3 also shows some color, but not as much, and an 80ED is color free to my eye. 

 

Color becomes less obvious at smaller apertures because the image is dimmer and the airy disk is larger.  With the 42.7mm aperture stop the color blur works out to 1.8 airy disk diameters, similar to my 110ED f/7 FPL-51 doublet (which, with its larger aperture, more readily reveals some color to my eye on bright white targets.)


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#20 ryanr256

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Posted 19 September 2019 - 10:18 AM

I don't know how people can't see the obvious color blur on short achros.  To me this demonstrates that people's color sensitivity varies far more than the optics themselves.  The calculated color blur of an 80 f/5 achro is ~6.3 times the airy disk diameter.  There is nothing subtle about it.   The Violet halo is readily apparent at a substantial diameter on Jupiter even at 67x.  By comparison an 80 f/11.3 also shows some color, but not as much, and an 80ED is color free to my eye. 

 

....

 

 

It's all about the rods and cones.

 

-Bob



#21 Redbetter

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Posted 19 September 2019 - 06:55 PM

It's all about the rods and cones.

 

There is more to it than that.  For example, a bigger player is yellowing of the eye lens with age.  And it is difficult to assess how much is judgment based in addition to differences in cone quantity, relative distribution, and such.  Some say it doesn't impact the image detail or that a yellow filter restores the detail for the aperture, but I haven't found either of those to be true.  From what I can tell experimenting with filters and such it isn't the wide outlier blue/violet or red that seem to do the most damage to fine detail to my eye, but some inevitable spread in the bluer-green through orange that are more apparent with the achros.  That is what I conclude from comparing details side-by-side at three different levels of color correction in the same apertures.

 

Back when the TV Pronto/Ranger was highly lauded I looked through one and was immediately struck by the violet halo--a nice achro, but an achro nonetheless.  It might have had glass that provided somewhat less CA than a traditional achro, but I wouldn't even classify it as semi-apo, despite being a 70.4mm f/6.8.  With a traditional achro's glass that would result in a color blur considerably less than an 80 f/5.   Perhaps it was somewhat better than that as they claimed some sort of "ED" glass, but it was clearly nowhere close to being an apo.  Even FPL-51 should have produced a near apo level of color correction for visual.



#22 Jim1804

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Posted 19 September 2019 - 10:59 PM

I don't know how people can't see the obvious color blur on short achros.  To me this demonstrates that people's color sensitivity varies far more than the optics themselves.  The calculated color blur of an 80 f/5 achro is ~6.3 times the airy disk diameter.  There is nothing subtle about it.   The Violet halo is readily apparent at a substantial diameter on Jupiter even at 67x.  By comparison an 80 f/11.3 also shows some color, but not as much, and an 80ED is color free to my eye. 

 

Color becomes less obvious at smaller apertures because the image is dimmer and the airy disk is larger.  With the 42.7mm aperture stop the color blur works out to 1.8 airy disk diameters, similar to my 110ED f/7 FPL-51 doublet (which, with its larger aperture, more readily reveals some color to my eye on bright white targets.)

I think we just don't spend a lot of time looking at objects with the ST80 that are going to show a lot of false color. I spent an hour or so with this scope tonight - worked my way up the chain of Messiers from the spout of the teapot, then over to Andromeda and finally the Double Cluster. None of those objects - which really shine in a short fl, wide-field scope - show any false color as far as I can see. But when I want to spend time on the moon or a planet, but still want small and super-portable, I bring out my C90 - no color at all, but of course a much smaller FOV. Right tool for the right job...


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