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.965 to 1.25 adapter - report

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#1 DeWayne

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Posted 30 September 2018 - 09:15 AM

I've picked up two long-focus 60mm refractors in the last six months, an 800mm Selsi and a 900mm Orion.  The first was a gift and the second was a junk shop find.  They are both Towa .965".  Everyone today is warned away from the "department store 60mm scope with the bad mount and .965 eyepieces" so I was skeptical when I received the Selsi.   But these older scopes were evidently the working model that the "cheap Department store scopes" were unsuccessfully trying to clone, because I've found mine to be delightful performers.  In fact, after rehabbing the Selsi earlier this summer, I went back and picked up the Orion at the junk store. That scope had been languishing for at least a year, and I'd looked at it before but rejected it because of the .965 format.  That scope had no working eyepieces but I had some .965s from the Selsi. 

 

One of first things you read about these scopes is "get yourself some 1.25 plossls" to replace the .965 eyepieces.   I'm offering a slightly contrarian modification to that advice - "Consider getting some plossls if you're not happy with the .965 eyepieces."  Last week I did get a .965 to 1.25 adapter to let me use my 1.25 eyepieces with the scope, and the results were not as definitive as I might have expected.  For others considering this situation, I'm offering this report on my work. 

 

Telescope Used:  The telescope I used was an Orion-brand Towa 60/900 refractor on an EQ2 mount.  It featured the original finder scope and diagonal.  It also had a locking screw on the drawtube to hold the diagonal. The locking screw is why I used the Orion scope instead of the Selsi, as the Selsi does not have a locking mechanism and the diagonal can slide out if overloaded. I was afraid the Selsi would not hold the heavier 1.25" eyepieces.  This photo shows the adapter inserted into the drawtube of the Orion 60mm.

 
20180925 181552

 

Eyepieces Used:  I've assembled a selection of .965 eyepieces including two presumably Towa Huygens 20mm and 5mm that came with the Selsi scope; a Meade MA40mm and SR4mm, and a "modern" 12.5mm no-name brand.  The diagonal is a prism that came with the Orion scope.  My test 1.25 eyepieces included an Orion Sirius 25mm, an Orion Expanse 20mm and 6mm; and a Meade Series 3000 16mm.  The test diagonal was a GSO mirror diagonal.  

 

Adapter:  My adapter is a no-name aluminum affair I purchased on Amazon. It has a .965 barrel that slips into the drawtube and a 1.25 receiver for the larger accessories.  For my test, I put the adapter on the 1.25 diagonal and then just swapped out the two diagonals for the test, using the adapter to fit the 1.25 diagonal into the .965 drawtube.  

Adapter
Here is the diagonal in the adapter in the draw tube.

20180925 181640

 
 

Test Targets:  Saturn and Epsilon Lyra (the double-double). 

 

Seeing conditions:  Test was conducted on 9/25/18 between 8 and 10 PM EDT, latitude about 30 30' N.  I live in a downtown and the skies were reasonably dark for my location -- about mag 3 naked eye, very calm.  The moon was beginning two wane and but probably did produce some sky glow.  These are typical conditions for my location.  I only get dark skies when a hurricane knocks out all our power (oddly enough, I seem to be the only one in my family who gets excited about this circumstance....)

 

Test Results: Saturn:  Saturn is putting on a beautiful show this year and I've enjoyed watching with my XT8 dobsonian and EQ90 refractor.  From my house, the refractor delivers an equivalent image to the much larger reflector; from a dark sky site, the reflector shows a brighter and more contrasty image.  I've also been surprised how sharp and clear Saturn looks with the little 60mm scopes. With either scope I can see the Cassini division easily, using the .965 eyepieces.

 

I started the test using the 20mm Huygens against the 20mm Expanse.  While there was a slight adjustment in focal length to account for the different light path through the 1.25 diagonal and adapter, these two yielded a more or less equivalent 45x. At that magnification, not much detail is visible, but I noticed the 1.25 image was brighter but not more detailed.  

 

From there I kept increasing the power by swapping out the eyepiece/diagonal combinations. I ended with a shootout between the 6mm expanse and the 4mm and 5mm .965 eyepieces.  The results were consistent throughout -- the larger eyepieces were brighter but not necessarily more detailed.  

 

Epsilon Lyrae:  One of my favorite showpieces (I guess everyone else's too?) the double-double is an easy test for optics. I usually look at these anytime I have my big scopes out and they never fail to please.  Prior to this night, I've never been able to split either pair with the 60mm scopes. Working my way up to the higher magnification, I was delighted to find I was able to split one of the pairs with the 6mm Expanse eyepiece!  Then I was more delighted to find I could split that same double with the 5mm Huygens!  I'd never done that before with the small scope.  I have two theories about this. 1) it was a darker and clearer night than I might have worked before and 2) once you see something, it's easier to see it again.  I've noticed this when comparing the Orion Nebula, Jupiter, and Saturn between the XT8 and the EQ90 refractor.  The larger reflector will cause a feature to really jump out, but when I look in the smaller scope, I can still see that feature but had not noticed it before. Possibly something like that was at work here. Certainly I've tried many times before to split the Epsilon Lyrae pairs unsuccessfully with that scope. 

 

 Conclusion:  The 1.25" eyepieces with the .965 to 1.25 adapter consistently provided a brighter image, though not more detailed.  Had I been able to test Jupiter, the contrast between the cloud bands might have provided a good test as well.  Having said that, the image was not so much better that I plan to use the 1.25 eyepieces from now on. In fact, I will probably continue to just use the .965 eyepieces, though it's good to have the option.  The adapter is so inexpensive that if you already have 1.25 eyepieces, it's a clear "why not?" decision to get an adapter.  

 

My expectations for the 60mm refractors are pretty limited.  They need to provide nice views of the planets, the moon, and some showpiece doubles from my downtown location. If I REALLY want to look deep and long, I've plenty of aperture and quality at my disposal for that, and that's especially true if I'm traveling to a dark sky site.  The 60mm scopes are a "quick peak" tool, even though a "quick peak" sometimes turns into an hour or more of looking.   These scopes serve a similar purpose to the Edmund Astroscan in that way.  

 

And I've found I kind of like the little "miniature" .965 eyepieces.  You can pick up good quality ones for a song, and the box of my entire collection (six now, plus a barlow) fits in the cargo pocket of my shorts.  Can't beat that for portability.  They must be kept pretty clean because they show dust badly, but I can work around that.  The lens design is simple and you can clean them yourself if you pay careful attention to which way the lens elements are pointed.  

 

I can't speak to the use of 1.25 eyepieces in larger scopes or Unitrons or something like that. But for relatively poor skies in urban locations, I'm finding the original-design .965 eyepieces are a good match for the smaller refractors and have some advantages over their larger 1.25 cousins.  Get the adapter, for sure, but I would say don't assume you can't have fun with the smaller eyepieces and get in some really enjoyable observing.  Certainly don't feel like you have to wait on the adapter to use the scope, or that the smaller eyepieces are useless, especially if they are the heavy old Japan-made .965s.  Take that old scope and its little old eyepieces out there, and see what you can see!  You'll be pleased, I bet.... 

 

 

 


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#2 respite

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Posted 01 October 2018 - 08:48 AM

Nice report. Thank you.

 

What about that 40mm?



#3 DeWayne

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Posted 01 October 2018 - 10:28 AM

Those are being sold on eBay as having "slight imperfections", and when you look through them you see various little speckles of black across the field.  Given that dust seems to be a perennial issue with these little eyepieces,  its not that bad,  just not pristine.  I thought it was air bubbles or schmutz in the glass itself, and kind of sad for an otherwise solid eyepiece.

 

However, the vendor shared with me the "imperfection" is actually just a design flaw in the arrangement of the lens resulting in the magnification of microscopic dust particles on the surface of the field lens.  When I took the lens apart and carefully and thoroughly cleaned it, most of the schmutz went away and I was left with a really nice 32 degree TFOV eyepiece.  It makes a great "finder" low power eyepiece.   In fact, I now have 3 of these.   One for each scope, and I glued crosshairs in the third one to use as a finderscope eyepiece.   


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#4 apfever

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Posted 01 October 2018 - 10:28 AM

The biggest issue with the type of adapter shown is how much it restricts the total light (vignetting) compared to a direct replacement of the eyepiece holding ring with a 1.25" holder. Granted, some .965" scopes have a draw tube that is not big enough to allow a 1.25" eyepiece barrel at all, and thus using a direct replacement ring is not possible.  I've found that the type of adapter shown tends to have a thicker rim for extra support of the intended larger heavier accessories. On top of that, it has to go Into the .965" holder.  These types of adapters are probably restricting the light into a 1.25" eyepiece even More than what is getting into the original .965" eyepieces directly. 

 

Here's a picture of two direct 1.25" rings, along with a .965" with a Thin walled eyepiece barrel installed. This is the difference in through put, but it gets a hair worse even.  The two stage adapter that uses the original .965" holder will ALSO move the 1.25" accessories further back in the light cone which will in turn even magnify the restriction caused. I do give kudos for the report in cases where a direct 1.25" ring won't fit or just isn't an option for the user.  For a newer viewer that may not be as understanding of the differences, I feel the difference needs showing and in the qualitative wording is HUGE. IMO.

 

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#5 DeWayne

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Posted 01 October 2018 - 10:40 AM

That all sounds reasonable to me.   There is a field stop inside my drawtube, so I was thinking the light cone is already so narrow by the type it reaches the diagonal,  that the restriction from my adapter-insert walls would not make any difference, as the cone is already narrower than the aperture of the adapter.   But I've never checked that.  It would be interesting to measure the size of the cone as it emerges from the drawtube...

 

Would the adapters you are describing fit on the outside of the drawtube, rather than being inserted inside? That's what I'm picturing in my head from your description.   I can see where that would remove any issue with restriction from the adapter itself.  Do you have a picture of one attached to a scope?


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#6 walter a

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Posted 01 October 2018 - 11:14 AM

I replaced my .965 with the vixen 1.25. [pic for reference]

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#7 apfever

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Posted 01 October 2018 - 01:00 PM

The adapter rings are male threaded to screw into the drawtube. Internal threads on the telescope are the standard so the adapter is made for what's common. I don't know of any 1.25" adapters made with female threads to go on the outside of the drawtube. I have seen external threaded drawtube (very rarely) that is a slip fit for 1.25" barrels, those have been plastic tube/focusers.


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#8 DeWayne

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Posted 01 October 2018 - 08:58 PM

Wow, that would be great if my tube took the adapters you've described.  I checked, though, and it has threads on the outside, and I think it's too small to receive a 1.25" adapter directly. I guess some other scopes have a larger drawtube to accept the larger adapters, as others have said too. My just won't take a 1.25" barrel.

 

Also, I checked the adapter barrel, and it is no thicker than the barrel of the .965 diagonal, so I don't know that I agree the 1.25 eyepieces were receiving even less light than the .965 eyepieces. To me, it seems like the light is either blocked by the .965 diagonal barrel, or it's blocked by the adapter barrel, but both eyepieces would receive the same amount of light, since the barrels are the same thickness. 

 

Regarding the idea that a longer light path is required by the adapter, I actually had to move the 1.25" set-up in an inch or so to achieve focus, so I would think that if anything, it was getting a little more light than the .965" set-up, though I don't know if that's enough to matter. I think the brightness of the image was just due to the superior design of the Plossl lens, not so much from the slightly shorter light path. 

 

In any case, my point was not so much that you shouldn't try to use the best equipment you've got, but rather don't let whatever equipment you have keep you from enjoying your telescope, especially if it was good-quality stuff to begin with, and its only crime was getting old. The difference between what I expected to see versus what I did see is what prompted me to post.  I expected a dramatic difference between the two systems - .965 v 1.25, and I did not see it as much drama as I expected. I thought others might find that interesting, too. Thank you to those who've explained why other scopes and other adapters might give a different result.  That all makes perfect sense to me.

 

If you are a camera person, it's like having a Rolleiflex and a Holga. I have both, and there is no doubt the expensive German Rolleiflex is a way better camera than the cheap all-plastic Chinese Holga.  But I've got binders full of negatives shot using either camera, because they each can be fun and useful in their way...  


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#9 claysshotgunner

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Posted 01 October 2018 - 09:25 PM

For my Jason 313, I bought a hybrid diagonal.  It seems to work very well for the 1.25.

 

But, I get just about as good a view thru the .965.  as the 1.25.  On the moon  they are dead even. Most of the planets are as good also


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#10 apfever

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Posted 01 October 2018 - 09:52 PM

How cool is this. Honestly, this just came in today. I caught our country carrier on his rounds and had a great fence chat. He's a traveling post office. Total cost out, shipping and everything included, international incoming, was $15 and change.

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Edited by apfever, 01 October 2018 - 09:56 PM.


#11 apfever

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Posted 01 October 2018 - 10:13 PM

This is in addition to the ones previously pictured.  They are an easy google search, all kinds of ads all over from the same company, varying prices depending on which ad where from the same company!.  I just clicked the $15 one then found out I chose basic minimal shipping with no return or refund or guarantee or tracking or anything. Only the upgrade shipping for another $5 gave any tracking or guarantee. OUCH! I was concerned. Turns out it came in on the early side, 12 days, official Vixen with cap, no problem. I just screwed it into the ATCO 80mm and it threaded like a glove right up to the stop. Looks like I might get some more.

 

DeWayne,  not exactly a biggie but racking in due to being further extended out is precisely what vignettes. You are pushing the pinch part further into a larger part of the light cone which is cutting off more of the cone. In a way this can help sharpen the view since the center part of optics tend to be the better more accurate area. Yes there are certainly some quality .965 eyepieces out there. I have some. I just sent off a Celeston pair, and have separated several others to my good shelf away from the newer cheap Dept. Store Foreign makes.  

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#12 sdedalus83

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Posted 01 October 2018 - 11:04 PM

DeWayne, the vixen adapter may work on the Selsi.  At $15, it's worth a try.

 

Unscrew the eyepiece holder and check the thread diameter. 36.4mm is what fits.



#13 memento

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Posted 02 October 2018 - 07:34 AM

Great report!

 

I also found that the old eyepieces are actually more than worth trying. They work really well in old achromat refractors!

 

Thomas


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#14 ETXer

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Posted 02 October 2018 - 09:37 AM

Thanks for the report! I use a standard .965 to 1.25" adapter for my classic orange C90. There is some slight vignetting, but for my strictly observational purposes it works fine.

 

Cheers, Allan



#15 konrad

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Posted 02 October 2018 - 10:17 AM

Thanks for the report! I use a standard .965 to 1.25" adapter for my classic orange C90. There is some slight vignetting, but for my strictly observational purposes it works fine.

 

Cheers, Allan

Get it bored out to 1.25 , thats what I did with my C5  works 100% better, there is plenty of metal to do this and one retains the thread 


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