52 replies to this topic

[Scott in NC]

Well, come on and join the party.  Or maybe someone nearby will take up DPAC testing.  Or maybe one of these days you’ll end up buying a scope that’s been previously DPAC tested on CN.  One of these days, I bet you’ll get your wish, one way or another.

[Jeff B]

Well done Scott and a nice sample.   Some mild zones and a trivial edge turn, but very good overall.

 

Achromats are different animals.  Secondary spectrum wise, right off the bat, you see the blue focus miss.   But also readily seen in the individual color images is the low level of spherochromatism, something slower achromats are good at.   But what clobbers the poly-Strehl is the secondary spectrum, especially with this sample, in the blue. 

 

Nice scope.   What do see visually....and what don't you see visually too?

 

Jeff

[Scott in NC]

Interestingly, the scope has a slow enough focal ratio (f/9.4) that it gives surprisingly good views on the planets and during white-light solar viewing. The first time I ever saw a Jovian shadow transit was through this scope about 18 or 19 years ago.  Sure, I know the CA is there, as evidenced by the test results I showed above, but I don’t find them distracting while observing.  And yes, my AT80EDL is a little better, but not by a huge amount, and in any case I’d expect it to be better for a scope that initially cost about twice as much as the SV80/9D did when new back in 2004.

[Most2]

I agree Scott with your overall assessment. I just ran across this thread and I too own an SV80/9D. Having had a fair number of fine APOs, I still use my SV80/9D scope frequently and find I still like it very much for open clusters, lunar observation and doubles. Quality for cost ratio is quite high actually and, with use, I have come to be quite fond of longish focal ratio scopes. Some scopes have that indefinable "itness" [my word, not found in the dictionary]. The SV 80 has "it" for me along with my SV102ABV doublet.

[Scott in NC]

Thanks for your input. Since I bought my first refractor (the SV80/9D) 20 years ago, quite a few fine achromats and apochromats have come and gone. But this remains on my “do not sell” list. It probably wouldn’t fetch much more than a couple hundred dollars on the used market, but it’s worth far more than that to me.

[Scott in NC]

Here’s my SV80/9D in the background ready to do white light solar observing along with my Lunt 60mm H-alpha scope. This picture is from last spring.

 

[gene 4181]

 I brought a guy into the astro fold with a SV 9 D and even when I show him the newer  availabilities, let him look thru it  he says, I'm good!   and I even have to exclaim, Wow thats a really clean  look thru it!   Where's my plosssls , orthos and Konigs, OH MY !   

[Scott in NC]

Mine has a nice 2” R&P focuser, and at f/9.4 I find that single-speed knobs are just fine. This scope is perfectly at home with my TeleVue and Pentax wide field eyepieces, so no need to go “old school” in the eyepiece department.

[Terra Nova]

Great report Scott. One thing is certain, regardless of the color channel, those lines are pretty much jailbar-straight. I don’t doubt it. I had one that I bought new in early 2003. It was a truly superb achromat. Chas always wants to crank up the power. I had my 80-9D on a Vixen GP mount with dual drives and cranked it up to 300X (both with a 2.5mm Vixen Lanthanum and also with a 7.5mm Ultrascopic and 3X triplet barlow) during the amazing Mars opposition that occurred at the end of summer/beginning of fall 2003. I did this on several nights just at dawn when the air was dead still. The views were amazing. I couldn’t believe how much detail I was seeing at 300X. The detail kept increasing all the way up to that point, it wasn’t lame magnification at 300X, tho it maxed out at that and showed no improvement in detail observed beyond that point. I think it was the best achromat I ever owned and I’ve been using refractors since 1965. The only other achromat that ever came close in it’s performance was another 80mm, an excellent Japanese Vixen 80mm x 900mm I used to own. Both are long gone, but the memories linger.

[peleuba]

Spherical correction looks pretty good in all colors (especially green), considering this is an inexpensive achromat produced nearly 20 years ago. Interestingly, I see a minor edge abnormality which doesn't really show up in the images shot in green light, but does show up in the image shot in white light, with the green channel extracted via image processing.  See here:

 

Anyone have any ideas as to why this might be?

 

 

There are a lot of ways to skin this cat...   but I never liked using software to "subtract out" or "extract" a color as the software does not tell you precisely which wavelength is being taken out.   And, its probably not a single wavelength but a range and this lack of specificity probably contributes to artifacts still being visible in the wavelength(s) that remain.  Also, the edge issue presented in your images is likely caused by two things: an actual edge problem AND diffraction effects.   In real life, its probably not as bad as what is shown in the image.   The proof of this would be to perform a star test and carefully examine the outermost ring for "hair".

 

The most accurate method I've seen is to use a gray scale image and subtract/extract the green, blue, red.  but still leaving the image in gray scale.  Moshen, years ago, showed me how to do this.  IrfanView is a terrific piece of software for this.

 

Finally, I am REALLY interested in the camera and new macro lens you have.  Can you share any details?  Your images are really quite good.

Edited by peleuba, 16 April 2024 - 08:42 AM.

[Scott in NC]

Paul, this thread is now a year old, but to the best of my recollection I used my Canon T2i DSLR with Canon 100mm f/2.8 macro lens. I don’t remember the settings, but probably somewhere around 1/60 - 1/80 sec with ISO 100-200. I’m sure of the camera and lens but the settings are just a guess.

[peleuba]

Paul, this thread is now a year old, but to the best of my recollection I used my Canon T2i DSLR with Canon 100mm f/2.8 macro lens. I don’t remember the settings, but probably somewhere around 1/60 - 1/80 sec with ISO 100-200. I’m sure of the camera and lens but the settings are just a guess.

 

I did not realize the age of the thread.. sorry.

 

What are you using now?

[gitane71]

I am just curious.... when I use a flat to test, the lens is out of the scope.  Do you check how tight the retaining ring is?  Does the lens 'rattle' just a bit in the scope?  Could the edge effect be just from a retaining ring that could be just a Bit too tight?  

??  

  Thanks

[davidc135]

I agree that the common slight turned edge effects are probably due to a mix of diffraction and real 'turned' edge effects. I put in the inverted commas because I wonder if the cause is often higher order SA. and not a fault in polishing.

 

I have a 75mm 'any three equal curves and a plane' achromat. I could test the edges of R1,2 and 3 against each other and R4 against a flat and all edges seemed to be in order with no tde and yet there is a slight but noticeable overall edge effect.

 

David

[Scott in NC]

I did not realize the age of the thread.. sorry.

 

What are you using now?

I'm still using the same Canon T2i DSLR, but most of the time I'll just use a Canon 50mm f/1.8 lens (not because that's necessarily any better than the Canon 100mm f/2.8 macro lens, but because the "nifty fifty" lens is what's often already attached to my camera, and this saves me the trouble of having to hunt around for anything else).

[Universe XY]

Stellarvue has the last of the lens cells for these listed for sale. 

 

Lists the glass as BK7/FK5 optical glass. Untested graded a to b.

 

They are 80mm f 9.4.

 

Curious what application could they be used for?

 

Could you put it into a shorter or longer telescope if it threaded in? 

 

Threads on to tube with male M90X1 thread

 

 

https://www.stellarv...aded-lens-cell/

[photoracer18]

Stellarvue has the last of the lens cells for these listed for sale. 

 

Lists the glass as BK7/FK5 optical glass. Untested graded a to b.

 

They are 80mm f 9.4.

 

Curious what application could they be used for?

 

Could you put it into a shorter or longer telescope if it threaded in? 

 

Threads on to tube with male M90X1 thread

 

 

https://www.stellarv...aded-lens-cell/

90mmx1 is the same thread used by the Vixen FL-80S CaF2 F8 Fluorite doublet.

[Universe XY]

90mmx1 is the same thread used by the Vixen FL-80S CaF2 F8 Fluorite doublet.

So Vixen maybe generally or some Japanese? 

Don't think this would be an upgrade to a Vixen Fluorite.

 

Might it fit in a 80mm f11 Celestron Power seeker not that I would want to spend $100 on it & the unknown when it's very usable as is.

Maybe only a scope shorter than f9 but not a f11 is could add extensions on focal tube?

 

Imagine it would be useless in a 80mm f6

[Universe XY]

Yeah, okay, but what I’m trying to show here is something that I can actually do on planet Earth, day or night, no matter what the weather. I’m glad that you have perfect skies most of the time, but I can’t hop on a plane with a scope and travel to your house every time I want to test out a scope.  You clearly don’t need to do DPAC testing, Chas, but I’m trying to let the other 99.9999999875% (that’s 1 minus (1 divided by 8 billion), multiplied by 100 to turn it into a percentage) of the world know an alternative way to evaluate a scope.

So then could you say at least in the objective you tested that the 80 9/SD has a very nice lens for an achro?

Stellarvue mentions that they didn't test these left over lenses & perhaps all of the scopes sold but are accessing the remainder left as grade a or b.

 

I will be the proud owner of a early Stellarvue 80 9/SD scope soon as long as the delivery gods shine kindly.

[RichA]

I'm still using the same Canon T2i DSLR, but most of the time I'll just use a Canon 50mm f/1.8 lens (not because that's necessarily any better than the Canon 100mm f/2.8 macro lens, but because the "nifty fifty" lens is what's often already attached to my camera, and this saves me the trouble of having to hunt around for anything else).

What does surprise me isn't that CA is prominent in  the achromat, but that at the highest levels, it's so well-controlled in the case of some apos, like AP or Tak's TOA scopes.

[kmparsons]

These tests are consistent with my experience. I got the SV 80 9/D when it first came out for a mere $349. I still have it and enjoy it. It impresses every time I use it. I can find some CA on some objects, but it is certainly unobtrusive. Stars are pinpoint to the edge. The views of DSO's like the Perseus Double Cluster are as as beautiful as any that I have seen of any telescope of that aperture. The SV 80 9/D would make a wonderful scope for a beginner, though it has probably been superseded by modestly-priced ED scopes such as the AT80ED. 

[Universe XY]

My Stellarvue arrives by UStork Postal Tomorrow.. $350 to $450 new... ooh paid $235 but its an oldie but goodie that needs some loving views in the sky///

[kmparsons]

My Stellarvue arrives by UStork Postal Tomorrow.. $350 to $450 new... ooh paid $235 but its an oldie but goodie that needs some loving views in the sky///

I think you will be amazed at the quality of the views you get from this modest achromat. 

[Universe XY]

Unpacked & ready for the mount if the mini porta holds it so have to be careful. I love looking at it for sure.

Beefy & the 80mm x750mm f9.4 looks like I will love the extra power & it's not too long as in a 900mm...

 

Has the black shiny retractable dew finder too.  Impressed by the build.

 

Nice shape for an old scope from a CN Classifieds. I think I'm addicted but could be worse drugs! 

 

Oh & found a Stellarvue M002C mount today on CN that will work on the bogen (Thanks Jon/TS) 

 

 

Edited by Universe XY, 08 May 2025 - 11:45 PM.

[Universe XY]

I think you will be amazed at the quality of the views you get from this modest achromat. 

I think so tool... Excited to get it up to the skies. 

 

Skies are clean & moon is right in perfect view. I'm famished though & have to get it mounted & balanced not sure the Mini Porta will handle it.

 

Took the 80 x 900... Have to be careful...