11 replies to this topic

[Scott in NC]

A Stellarvue SV105T (105mm f/7 apochromatic triplet) caught my eye the other day, and it arrived today in great shape. Some of you are probably wondering why I would buy this when I have plenty of scopes already. Well, my son has been having such a good time with his recently acquired Tak FS-60 that I decided he needed a 4" apo to complement it. And this one just happened to come along at the right time for a great price, so I couldn't resist.  It's cloudy tonight, but this gave me the perfect opportunity to DPAC test it to make sure it was going to meet our expectations. To the best of my knowledge, this scope's optics were figured in China from Ohara FPL-53 glass from Japan, then tested by Stellarvue in Auburn, CA to make sure it met SV's specs. This was produced during the generation of Stellarvue apos that came between the older generation with Russian-made LOMO and LZOS optics, and the newer "SVX" generation with optics made by Stellarvue in the U.S.  

So here's a pic of the scope set up on the optical bench, ready for testing.

 

[Scott in NC]

At first I couldn't get the scope's optics precisely orthogonal to the optical flat in order to get the best test images, so I removed the dew shield and tried again. Fortunately, the dew shield was very easy to unthread, and this time everything lined up perfectly.

 

[Scott in NC]

Now for the test results.

 

Green inside / outside focus:

 

 

Red inside / outside:

 

 

Blue inside / outside:

 

 

White inside / at / outside:

 

[Scott in NC]

Unlike the first iteration of Stellarvue's latest generation SVX apos, this scope appears to be best corrected in green. Red has slightly more spherical aberration, and blue is the farthest off. As has been stated many times before on this forum, green is where you really want a refractor to exhibit the best correction, especially in a scope meant for visual use. The "at focus" image looks pretty smooth, and I don't see any major zones, nor edge aberrations.  Chromatic aberration is nicely controlled for an f/7 refractor.

 

Now all that remains is to take this scope out under the stars whenever the weather clears up.  So far though, I'm quite pleased, and feel that this scope was a good purchase.

[Kitfox]

It must be said...You're an awesome dad, Scott!!!  

 

That sure looks like a really nice lens.

[EGregerson]

Well... i thot my SV105T was perfect.    I have sn00508;   Assy by SC; Star Test by SC; star test by Vic. So do u suppose the test would have been DPAC?  or other?   I think u/ur son will really enjoy it.  

[Rockwood]

Hi Scott

Nicely done. You certainly have come a long way since starting your DPAC journey in Feb/23. Keep posting your results.

Rock

[Scott in NC]

Well... i thot my SV105T was perfect.    I have sn00508;   Assy by SC; Star Test by SC; star test by Vic. So do u suppose the test would have been DPAC?  or other?   I think u/ur son will really enjoy it.  

Thanks for your input. I don’t have inside info into what Stellarvue does, but I’ll assume that the star test was done indoors with an artificial star, although I do recall Vic reporting in years past that they were often done outdoors using a real star. I don’t think that SV did any DPAC testing until about a year ago, after CN member peleuba demonstrated the value of DPAC testing, soon after which they incorporated that into their repertoire of testing. SV may or may not have had a Zygo interferometer for some of their testing back then, but I don’t really know for sure.

[Scott in NC]

Hi Scott

Nicely done. You certainly have come a long way since starting your DPAC journey in Feb/23. Keep posting your results.

Rock

Thanks, Rock. It’s been a fun and educational journey over the past 14 months. One of these days I’d like to go back and redo some of my earlier tests, as my equipment and photographic technique has evolved a bit since then.

[PhotogTom]

At a glance, I'd say that this is a very good optic! Your son should be very happy with it.

 

Oh, and do you mind if I call you dad?

 

And I'd like to remind you that I don't have anything larger than a 130 mm....

[kgb]

Nice test! I keep buying my son new telescopes too. He is 7 and doesn't have much interest in Astronomy yet, but I am keeping them safe and warm until he is ready. 

[dryfly]

Nice looking test.  You have a lucky son.

 

Mike