724 replies to this topic

[Jeff B]

Or take a pause as DPAC Nervosa can quickly set in.   

 

Rest, meditation and beer and or bourbon can all help.

[Scott in NC]

I'm already obsessed.  Not that you guys could tell.

[Maciek_Cz]

Thank you so much—I’ll check out that link after I get home from work tonight!

If you have any problems with installing or using the program, feel free to ask.

AOS works under Windows, .net 6 is required for its installation, which is installed during the installation of AOS.
I'll be glad to see someone using this tool.

In fact, it's interesting to see if anyone besides Jeff uses it.

Maybe thanks to your enthusiasm I will catch another user...

Edited by Maciek_Cz, 20 February 2023 - 02:02 PM.

[Scott in NC]

Oh no, it just occurred to me that my home computer is an Apple MacBook (which of course uses iOS).  I’ll have to see if I can use my wife’s or son’s Windows laptop or else my Windows PC at my office to try AOS out.

[Scott in NC]

Now this one was a bit harder because the opening of the dew shield is larger than the size of 6" flat, making it much harder to get aligned.  I had to fiddle with it for a while but finally got it.  I really need to construct a platform to hold the flat, as the whole time I was doing this I was worried that the flat would fall over and get damaged.

 

This is my Takahashi FS-128 fluorite doublet, and I found the results to be rather pleasing.  Not 100% perfection, mind you, but pleasing nonetheless.

 

[Scott in NC]

Takahashi FS-128 f/8 fluorite doublet

 

Inside focus:

 

 

At focus:

 

 

Outside focus:

 

[Scott in NC]

Sorry for the dim images, but I had to use a faster shutter speed as the image was shaking over the place due to the long, heavy tube balanced on its dovetail plate on the dining room table.  Now I see why some of you use V-blocks.  Also, ignore the horizontal streak on the at-focus image, as that was a reflection off the camera lens.

 

I see very good edges, and maybe a tiny hint of overcorrection.  I can't decide on this for sure, as I only notice it on the outside-focus image (and just barely at that).  I can't say that I really see any definite band curvature on the inside-focus image.  And I can only see this when focusing out to 3 bands, not to 4-5 or more.  You know you're really getting obsessed when you feel the need to get a straight-edge to check for sure, and I think I’m going to try this.  But I think the bottom line is that if the lines are so straight that you can't decide for sure whether they've got the tiniest hint of a curve or not, then the scope probably has pretty decent spherical correction.

 

Edit: If I enlarge the outside-focus image so it fills a large portion of the screen on my iPad and then hold a straight-edge up to the sides of the outer bands, I can indeed detect a very minimal amount of curvature. When I do that for the inside-focus image I still can’t say for sure that I see any definite curvature, but I’m not sure how the outside-focus images could show SA and not the inside-focus images.  Regardless, I’m very pretty pleased with this optics set, both with the actual star test and with the DPAC results.

 

Comments, anyone?

Edited by Scott in NC, 21 February 2023 - 09:08 PM.

[peleuba]

 

Comments, anyone?

Looks like the aperture is being cut off.  The photo is not perfectly round.  The flat may need to be slightly elevated for this scope.    Nevertheless, this scope in green seems like a solid eighth wave.   Very nice.  It may be worse in red and blue.   But green looks very good.

Edited by peleuba, 21 February 2023 - 10:09 PM.

[Scott in NC]

Yeah, I was wondering if anyone would catch that.  I really need a platform to hold the flat, as I had a heck of a time even getting it lined up that well.  Thanks, Paul!

[Kitfox]

I just casually got online and looked at Edmund Optical's flats.  I couldn't get out of there fast enough, all my credit cards combined don't have enough credit limit...

Edited by Kitfox, 22 February 2023 - 01:07 AM.

[Scott in NC]

I just casually got online and looked at Edmund Optical's flats.  I couldn't get out of there fast enough, all my credit cards combined don't have enough credit limit...

Yeah, they’re pretty expensive at Edmund.  Don’t worry, I didn’t buy mine from them, and didn’t pay anywhere near their prices.

[peleuba]

Yeah, I was wondering if anyone would catch that.  I really need a platform to hold the flat, as I had a heck of a time even getting it lined up that well.  Thanks, Paul!

You could also unscrew and remove the dew shield to get the the lens closer to the flat to make alignment easier.

Edited by peleuba, 22 February 2023 - 06:31 AM.

[Scott in NC]

You could also unscrew and remove the dew shield to get the the lens closer to the flat to make alignment easier.

Of course…somehow the obvious escaped me last night. I still plan to try to find some materials for a flat holder and some V-blocks this weekend.

[Jeff B]

Sensi Paul made a great suggestion in my CFF 92 DPAC thread to share some of my techniques for capturing and processing my images.  

 

These have evolved as my "rig" and "abilities" have evolved. They are specialized for my situation and needs, but there is some generic stuff too.

 

1.  Keep at it and experiment, "It works the more you work it and the more you work it the more it works for you."  

2.  Develop your system and capabilities to suit you wants, interests, and needs.

3.  Post what you're doing and invite comment...and you'll get plenty, and don't be afraid of making mistakes in public.  I've found I learn the most  when I make mistakes and folks call me out on it.  Don't equate ignorance with being dumb.

4.  Keep your ISO slow (reduces noise, I use ISO 50), your exposure short but long enough to get good brightness and detail but not so long as to get image blooming. 

5. Keep the LED brightness "comfortable" to your eyes.  Typically, if your eyes are comfortable with the brightness, your camera will be too (meaning you won't saturate the sensor.

6.  I turn off auto-focus and focus manually and use the image stability feature if your camera has it.  

 

I use my older cell phone as it has an excellent camera with excellent optics and all-kinds-of-adjustments (I found my fancy DSLR frustrating to work with).   It's sensor is rather blue sensitive so I choose a "warmer" white light LED, set my white balance to warm, and keep my LED brightness comfortable, all to keep from saturating the sensor in blue, though I have to be mindful of red saturation/blooming too.  I find the effects of sensor blooming more destructive on the lower contrast, inside of focus images.

 

Now, I use a "white" LED to take my "master images" for the inside/outside of focus shots.  I then use an ancient version of Paint Shop Pro to isolate/filter the individual red, green and blue channels.  I double filter each channel in PSP to better isolate each color.  I can also blend the channels to form yellow (basically cutting the blue channel out) and orange (cutting out the blue and 50% of the green) images...and even purple, which is not a color, but can be really interesting and will be the subject of another thread.

 

I use a white LED and split the colors because:

 

A.  It's soooooo easy and quick.

B.  When carefully done I get basically identical results to using individual LEDs.  Attached is an example (green LED image is actually a bit oversaturated). 

C.  It's sooooo easy and quick.

D.  Since the colors originate at the same time, from the same source, in the same position along the light path, I can get direct intelligence as to a refractor's color correction, both longitudinal (color focus) and spherochromatic, all from one master image.  This can, and does, help explain what I see, or don't see, at the eyepiece in terms of color correction.  This technique is also helpful in showing the color errors & filtration that most bino-viewers introduce.

 

As my phone is hand held, tilting of it will show up as R/L or up/down difference in thickness of the ronhi bands.  I just keep banging off shots (with motion stability on) until I get even bands as best I can (code for throwing away about 90% of my images.)  I've also found that camera positioning outside of focus is much more sensitive than inside of focus for faster scopes.   I don't know why.

 

My screens also have some lateral play in their scratch built holders. This allows me to nudge them around, trying to position one Ronchi line so that it goes right through the middle.  I focus for 3 lines, but also, for refractors, I'll let lines just start to creep in from the sides as this helps me see color correction with a white light image.

 

Now I do use a single green LED to capture the at-focus images for refractors because the other colors can interfere, make finding focus difficult, especially with an achromat.  I'll position a line right in the middle while slowly approaching focus and nudge it around to keep it there until the view goes completely dark from the line's shadow.  I'll nudge the screen so that it acts like a KE, tweaking it and focus, until I get the ugliest, fully illuminated view I can get with reasonable brightness.  Then I take pictures.  The at focus images are the only images where I will manipulate brightness and contrast to pull out wave front details.

 

I frame and crop each image to a "standard" size which works for me.

 

Jeff

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Edited by Jeff B, 22 February 2023 - 02:13 PM.

[Scott in NC]

Thanks, Jeff.  This is very helpful. 

[Scott in NC]

I figured out a better way to set up my FS-128 for testing (thanks for the tip, Paul!).  Now the reflection off the 6” optical flat will fully illuminate the scope’s objective lens.

 

 

[Scott in NC]

Time to go outside and grill some NY Strip steaks, but more to come later!  Stay tuned…

[Scott in NC]

Wow those steaks were good!  Okay, back to the subject at hand. 

 

FS-128 f/8.1 fluorite doublet

 

Inside focus:

 

 

 

At focus:

 

 

 

Outside focus:

 

[Scott in NC]

I've been playing around with the intensity of the green LED light, and camera focus, exposure, and ISO, and I think I'm getting cleaner, brighter images than before.  Not that that affects what the test results ultimately show, but it does make the images easier to interpret IMO.

 

On the FS-128 I see a hint of overcorrection and a very slight downward turn of the lens edge.  I think it looks slightly better than the FS-102 did, but my camera settings were different when I tested that scope, so it may not be possible to directly compare the images that I've presented here.

 

Comments?

 

Edit: Rereading this a month later, I see that I inadvertently wrote the direction of the turned edge backwards, and I’ve corrected it for accuracy.

Edited by Scott in NC, 23 April 2023 - 09:09 AM.

[Alan S]

I've been playing around with the intensity of the green LED light, and camera focus, exposure, and ISO, and I think I'm getting cleaner, brighter images than before.  Not that that affects what the test results ultimately show, but it does make the images easier to interpret IMO.

 

On the FS-128 I see a hint of overcorrection and a very slight upward turn of the lens edge.  I think it looks slightly better than the FS-102 did, but my camera settings were different when I tested that scope, so it may not be possible to directly compare the images that I've presented here.

 

Comments?

99% of what I know about this, I have learned from following your adventures. I would agree with your assessment. Take that for what it’s worth!

[Scott in NC]

99% of what I know about this, I have learned from following your adventures. I would agree with your assessment. Take that for what it’s worth!

Thanks, Alan.  Guys like Paul, Jeff, and David are the real gurus on this subject, and I’ve learned an incredible amount from them just over the past week.  I so greatly appreciate their tutelage, and one day I hope to be able to help others as much as they’ve helped me here.

[Scott in NC]

Now onto my Stellarvue SV115 f/7 TMB/LOMO triplet.  I believe this one was created in 2006, and I’ve owned it since late 2020.  It’s one of the few that was produced with an anodized (rather than powder coated) tube.

 

Optically I’ve found it to be exceptional for its aperture.  Yes, it’s larger than many refractors, but it’s still only a 4.5” scope. One night a couple of years ago when I had it outside the same night as my former TEC140ED, I recall that Mars was one of the objects of interest, and I really couldn’t tell much difference between the views from either scope (resolution wise, that is, as the TEC’s views were of course slightly brighter).

[Scott in NC]

SV115 f/7 TMB/LZOS set up for DPAC testing

 

 

 

 

 

[Scott in NC]

SV115 inside focus:

 

 

 

At focus:

 

 

 

Outside focus:

 

[Scott in NC]

I think I'm seeing a touch of overcorrection again.  And maybe a very tiny degree of turned down edge?  In this case I can't tell with 100% certainty whether that may be more of a diffraction artifact from the photo, but since the smudges or "hooks" appear to turn slightly outward in the inside-focus image and slightly inward in the outside-focus image, I'm going to go with a very slight turned down edge.

 

So this just goes to show you how sensitive DPAC testing is (magnifying errors two-fold, hence the D for double in "DPAC"). Every single scope that I've presented here has given me very nice views of the heavens, and I'm still pleased to own them all.  And as you've seen, none of these fine scopes scores a perfect 100% for optical perfection during DPAC testing. Doing this certainly isn't for the faint-hearted, or for those whose egos will be crushed if they find out that their prized scope isn't perfect.  I would not recommend doing it on a scope that you've never actually viewed through before (unless you’re testing it for someone else who has viewed through it before).  I also don't think that it would be a good idea for an absolute beginner to astronomy to start testing right away, especially if this person doesn't have any experience with either visual observing or AP.  The bottom line is that even in very nice premium scopes, you're going to see deviations from perfection that won't even show up on visual observation.  Maybe they'd show up during high-magnification planetary AP, or maybe even during high-magnification visual observation on the most perfect of nights with 10/10 seeing.  I wouldn't know, as I don't ever seem to get those nights, or if I do, they don't line up with nights when I'm off work and am free from other obligations.

 

This whole process has been very educational for me, and I thank those of you who have borne with me and followed my progress.
 

Edit: Rereading this a month later, I see that I inadvertently wrote the direction of the turned edge backwards, and I’ve corrected it for accuracy.

Edited by Scott in NC, 02 July 2023 - 06:53 PM.