Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Tricks and techniques in even illumination and processing a full disk?

  • Please log in to reply
58 replies to this topic

#1 chemman

chemman

    Apollo

  • -----
  • topic starter
  • Posts: 1,142
  • Joined: 21 Jun 2011
  • Loc: Colorado

Posted 25 November 2021 - 03:12 PM

Image using LS100MT-DS of the sun.  360 images from ASI1600mm staked in Autostakkertt 3 best 25%.  No other processing. 

Wanting input on how best to get even illumination.  Using a 2x Siebert Optics Focus adapter that has T2 adapted 110mm of "eye relief" for filters and such. I have a SmallRig 15mm optical rail that can mount on the back of the dovetail plate to support the camera but with T2 extension barrels from the 2" Barlow in the focus barrel all the way to the camera, all is pretty secure. Always use straight through ie. no diagonal.  Seems like even illumination changes during long capture sessions.  With 3Tb storage on the telescope's onboard capture and control computer about 2-3 hour sessions are a normal day. 

Even illumination and processing a full disk are the goal here. 

 

Thanks
Chuck

 

get.jpg?insecure

 

5bE0ls2.jpg

 


  • philmor56, ifly and hamers like this

#2 MalVeauX

MalVeauX

    Cosmos

  • *****
  • Posts: 9,740
  • Joined: 25 Feb 2016
  • Loc: Florida

Posted 25 November 2021 - 03:29 PM

Hi Chuck,

 

Two major factors are at play that you can effect. 1) Position of the disc relative to your sensor, ie, move the disc around until the most even disc is seen, it's not always exactly centered. 2) Etalon tuning for being both on-band and with the least interference from too much tilt and/or pressure, it's really hard to go through the entire tuning range in tiny steps since these are not motorized (some are!). But it helps loads to be as gentle as possible and move through the tuning range for best even uniformity which should result in even illumination. The variable illumination is due to uniformity being variable. Going back and forth between tuning your etalon for best uniformity and moving its position on your sensor to get the best result somewhere on your sensor will be a dance, but will result in an even disc unless your etalons simply are not uniform. It's hard with 2 etalons, double stacked, because any issues with uniformity and/or tuning will be exacerbated.

 

I would start the above without a barlow or amplifier; do it at native image scale of your scope on your sensor so that you have as much wiggle room as possible. Resolution isn't important for this stage of figuring out how to tune your etalons ideally and where on your sensor the disc needs to fall for best results (will be different each time you move your imaging train, secondary to tilt and sag even if only minute amounts). I would also do it with one etalon first and get a good example of an even disc from one etalon so that you can see what you have on-band and with what uniformity your filter has, when on-band. Get that nailed down before moving to having two etalons doing it. It takes a lot of practice and back and forth, no way to automate this at this time on these current instruments without steppers and micro-scaffolding.... maybe one day!

 

The top right of your disc in its display orientation is going off-band, which is why it's getting brighter, so you're at the edge of the sweet spot there relative to your etalon(s) at their tuning and orientation. So I would move the disc away from that area, so moving bottom left a bit with it. If you can't do that without losing FOV of the disc, just reduce image scale a bit (such as 1.5 or 1.6x barlow or no barlow) until you can see your disc both on-band and with even illumination. If you're using front mounted etalons, then it's virtually always going to be a tuning issue (relative to sweet spot, since the sweet spot will be very large), so you'll have to practice more with tuning one etalon, then two, to get both on band and even illumination relative to each other which may involve some rotating of the etalon so that any tilting is complimentary and not counter productive. I find pressure tuning much easier, due to this, despite front etalons being superior for full discs.

 

Very best,


  • chemman, lorenzo italy and IR656nm like this

#3 MalVeauX

MalVeauX

    Cosmos

  • *****
  • Posts: 9,740
  • Joined: 25 Feb 2016
  • Loc: Florida

Posted 25 November 2021 - 03:38 PM

By the way, happy Thanks Giving solar friends!

 

Very best,


  • BYoesle, chemman, B 26354 and 2 others like this

#4 IR656nm

IR656nm

    Explorer 1

  • -----
  • Posts: 87
  • Joined: 12 Mar 2018

Posted 25 November 2021 - 05:29 PM

Hello Marty,

 

I forgot it is Thanksgiving! in the US.

 

Happy Thanksgiving, Marty and family.

 

Best wishes and thanks for all your solar imaging advice over the years.

 

Magnus


  • chemman, MalVeauX, hamers and 1 other like this

#5 rigel123

rigel123

    ISS

  • *****
  • Posts: 20,598
  • Joined: 29 Jun 2009
  • Loc: SW Ohio

Posted 25 November 2021 - 08:56 PM

What Marty said, and one minor addition, crank up your gamma as that highlights the variations on the disk.  Typically you will see the center of the disk will be a bit brighter with a uniform darker limb all the way around when you are centered in the sweet spot.  Then turn off gamma and take your shot.

 

Happy Thanksgiving!


  • chemman, torsinadoc, lorenzo italy and 1 other like this

#6 chemman

chemman

    Apollo

  • -----
  • topic starter
  • Posts: 1,142
  • Joined: 21 Jun 2011
  • Loc: Colorado

Posted 26 November 2021 - 12:49 AM

Happy Thanksgiving everyone!  I was happy to provide the family 22 pounds of turkey smoked 20 hours with Hickory, it was great.  

 

Marty, both my etalons are pressure tuned and I am sure I had become lazy not retuning between days shooting.  With my current setup I plug in the GEM45 handbox and GPS. Put the scope on the mount careful to not move any bits and pieces.  Plug a 12vdc plug into the on board computer, Gem45, and PrimaluceLab focuser. Power up the mount and computer and use the handbox to GOTO the sun. Push the Finder button on the Hinode Guider and use the GEM45 handbox to get the highest pitch tone.  Go inside and connect to the scope with VNC, start Sharpcap, HinodeSG, and Sun Scintillation Monitor for the AiryLabs.  Select the ASIXXXmm and have an in focus image of the sun.  Notice I left out the "Tune the Pressure Tuners" step.  My bad on that.  I can typically get a quite satisfactory image on the camera.  But like you noted, that section is off band.  Sometimes the image is tuned in across the FOV sometimes not.  Temperature, angle in the sky, tuning and a few other weird or unknown factors play a part in whether the image across the FOV is on band.  I really want to get a precision pressure control for the two internal pressure tuned etalons on my LS100MT but Lunt has not been able to supply one.  I have had a manifold ready complete with Lunt's PT adapters but have not brought myself to risk a mistake with pressure loss of control.  I would hate to blow an etalon up.  

 

I have been working toward analyzing the images I get at critical sampling for the ASI174mm f/21 and the ASI1600mm f/14.  I have yet to put the images side by side so see if one is "better" than the other.  The 174 gives about 1/4 disk and the 1600 give a full disk but much more difficult to deal with image datasets.  Currently I am waiting on 120 32mb 16mp images to import and align into Photoshop. 

 

Warren, I will have to incorporate gamma into my imaging, have really never used it.  So far the ASI174 seems much easier to image with in all aspects compared to the ASI1600.  I started using the 1600 and had issues with Newtonian Rings galore, mostly >f/14.   Ironically the ASI1600 at f/14 and the ASI174 at f/21 really show hardly any Newtonian Rings.  Go Figgure.  

 

Here is the entire day's frames.

 

https://youtu.be/Xn9henVvUlA

 

get.jpg?insecure


Edited by chemman, 26 November 2021 - 12:53 AM.

  • MalVeauX likes this

#7 rigel123

rigel123

    ISS

  • *****
  • Posts: 20,598
  • Joined: 29 Jun 2009
  • Loc: SW Ohio

Posted 26 November 2021 - 07:05 AM

Halfway into your animation the disk appears to be centered in the sweet spot.  Those are the frames I would use for the full disk.


  • chemman and torsinadoc like this

#8 chemman

chemman

    Apollo

  • -----
  • topic starter
  • Posts: 1,142
  • Joined: 21 Jun 2011
  • Loc: Colorado

Posted 26 November 2021 - 07:25 AM

Halfway into your animation the disk appears to be centered in the sweet spot.  Those are the frames I would use for the full disk.

I have been making a habit of logging my seeing and using that to choose the best captures.  Not sure how to nail down that sweet spot.  It seems more forgiving at times than others.  Temperature and angle seem to play a part there.  It definitly calls for practice remotely tuning the etalons.  It took alot of practice to get remote focusing down to a science for sure.  

 

Chuck



#9 MalVeauX

MalVeauX

    Cosmos

  • *****
  • Posts: 9,740
  • Joined: 25 Feb 2016
  • Loc: Florida

Posted 26 November 2021 - 07:52 AM


I have been working toward analyzing the images I get at critical sampling for the ASI174mm f/21 and the ASI1600mm f/14.  I have yet to put the images side by side so see if one is "better" than the other.  The 174 gives about 1/4 disk and the 1600 give a full disk but much more difficult to deal with image datasets.  Currently I am waiting on 120 32mb 16mp images to import and align into Photoshop. 

 

This comparison will only be comparing seeing condition differences; the sampling is essentially identical and after stacking 40 or more frames, there's no appreciable noise profile to study. The true differences will be simply due to lucky imaging in variable seeing conditions when comparing images. So I wouldn't put too much effort into this. The generation tech in those sensors is close enough to not worry about it. If they were 10+ years apart, that would be different of course. Your IMX174 is great for partial disc sampling at fast FPS, your MN34230 is great for full discs, but is equally good for partial disc sampling at faster FPS; just reduce the FOV via ROI and collect from less pixels. This would be important when seeing is variable or poor. When seeing is excellent, F14 in HA on that sensor is going to have the same resolution whether its full disc or partial disc because its critically sampled. You likely don't need your IMX174 at all at this stage, because your MN34230 can already do everything the IMX174 can do, but with more sensor real estate to work with. As you know, your data size is going to be immense with that sensor, but that's part of it. It's easy to chew through big data with modern chipset architecture, modern CPU and fast memory and SSD, it makes a big difference with a more moden platform.

 

Very best,


  • chemman likes this

#10 chemman

chemman

    Apollo

  • -----
  • topic starter
  • Posts: 1,142
  • Joined: 21 Jun 2011
  • Loc: Colorado

Posted 26 November 2021 - 08:25 AM

Before deciding to get the 174 I was really wanting something to get a full disk at f/28 and running at 200fps and 8k.  That was proving to be extremely expensive and likely impossible at any price.  7.5um pp at 35mm square and 8k 200fps is a Spielburg budget pipedream.  

 

I decided on the much more affordable 174 to critical sample at f/21 and with a smaller senso apparent amplification and frame rate would hopefully be acceptable and it is.  With accurate framing and tracking Full HD id good on active regions and Prominences. 

 

I was getting good results with the 1600 at f/21 and f/28 and could get higher framerate by using aoi but knew my critical sampling was suffering.  In addition it was very hard to not use all 16mp.  2x2 did not seem to do much for critical sampling either.  The 174 has the added bonus of smaller datasets especially when running all day every 20 or 30 seconds.  

 

With your advice Marty I will quit comparing the two and run with the advantage each offers.  Atleast until I can afford a RED HELIUM.  lol

 

Chuck



#11 MalVeauX

MalVeauX

    Cosmos

  • *****
  • Posts: 9,740
  • Joined: 25 Feb 2016
  • Loc: Florida

Posted 26 November 2021 - 08:38 AM

Before deciding to get the 174 I was really wanting something to get a full disk at f/28 and running at 200fps and 8k.  That was proving to be extremely expensive and likely impossible at any price.  7.5um pp at 35mm square and 8k 200fps is a Spielburg budget pipedream.  

 

I decided on the much more affordable 174 to critical sample at f/21 and with a smaller senso apparent amplification and frame rate would hopefully be acceptable and it is.  With accurate framing and tracking Full HD id good on active regions and Prominences. 

 

I was getting good results with the 1600 at f/21 and f/28 and could get higher framerate by using aoi but knew my critical sampling was suffering.  In addition it was very hard to not use all 16mp.  2x2 did not seem to do much for critical sampling either.  The 174 has the added bonus of smaller datasets especially when running all day every 20 or 30 seconds.  

 

With your advice Marty I will quit comparing the two and run with the advantage each offers.  Atleast until I can afford a RED HELIUM.  lol

 

Chuck

I recall your quest for 4k~8k at fast FPS. The tech is out there, just not mainstream for this application yet. Yet it's in phones lol.

 

So, your IMX174 critically samples at F21~22 in HA at max FPS but the area of view is small. Your MN34230 critically samples at F14 with slower FPS, but if you crop the ROI to match the same FOV as your IMX174, it will be a better comparison and you could see what FPS that sensor will achieve there. When critically sampled and at the same FOV, the look and resolution will be essentially identical. Using the MN34230 at F21~28 is vast oversampling for HA, so you don't gain resolution all doing that, and simply lose light to stretching the image as you magnify it without a gain in resolution, so you end up potentially needing more gain and slower exposure values which is counter productive for lucky imaging and high resolution sampling. Binning will do nothing for it either because you increase the effective pixel size for sampling purposes and then you have to use longer focal-ratio to properly sample, but it will not be better, it cannot be, you can already sample without binning perfectly, so there shouldn't be an improvement that you can appreciate when binning and using longer focal-ratio. Your MN34230 is a total replacement frankly for the IMX174 and will give you a full disc. For high res, just reduce the ROI to a smaller area and benefit the faster FPS for when imaging a particular area or making an animation, etc, as more FPS in shorter time is preferred for that, if you're not needing the full disc view. I know its hard to not use the full large sensor, but you'll find you can still get a great large image and much faster FPS and you'll get potentially better data simply from faster FPS and lucky imaging, getting more odds on good data when seeing moments are good.

 

Very best,


  • chemman likes this

#12 BYoesle

BYoesle

    Fly Me to the Moon

  • *****
  • Posts: 7,299
  • Joined: 12 Jun 2004
  • Loc: Washington USA

Posted 26 November 2021 - 09:58 AM

Hi Chuck,

 

That's a pretty disappointing full-disc image. Even if you were able to use flats or other tricks, there would be significant bandpass variations of the underlying detail.

 

A couple of things to consider. When you double stack, the reduced FWHM of the filter system decreases the size of the Jacquinot (aka "sweet") spot. For a front mounted air-spaced etalon, the Jacquinot spot goes from about 1 degree for a single 0.7 A etalon down to about 0.84 degrees when double stacked. See here. Both will easily fit the entire solar disc and then some in a field of relatively uniform spectral response and therefore contrast uniformity.

 

However, when one places the etalon in a collimator optical system, the magnified field angles reduce the size of Jacquinot spot via the amount of magnification. A collimator lens with half the focal length of the objective will double the magnification, and shrink the spot by a factor of 2 - or 0.5 degree which will barely fit a solar diameter for a 0.7 A etalon. Double stacked this will be 0.42 degrees, and thus a full disc with good contrast uniformity is not possible. Due to optical geometry for the etalon size, the etalon would have to be no less than 50% the diameter of the objective to maintain good full disc contrast performance for a single stack, and would need to be even larger with a longer collimator FL for the narrower FWHM of the double stacked system. To add to the complexity, in your system you are dealing with two sets of collimator and refocusing lenses, which may exacerbate the reduction of the Jacquinot spot even more than a narrower FWHM system would otherwise do by itself. It may also be that in the new Lunt modular telescope designs the collimator(s)/etalon(s) have been configured differently than in the previous dedicated telescopes, as I don't recall the Jacuinot spot being as obvious in the LS100THa images I have seen.

 

Additionally, from your image the Jacquinot spot and optical axis lies off of the mechanical axis of the system. When you state your using "straight through" it is not clear if you're referring to the blocking filter. If not, most of the off-center issue is likely due to the diagonal blocking filter (and sometimes to a lesser extent the focuser alignment), and a straight through BF is therefore recommended. It might also be the case that the second collimator/etalon system involves some tilt to remove ghost reflections, which would also result in an optical axis offset. Also apparent is that the center of the Jacquinot spot is slightly off-band, and produces a "bulls eye" ("sweet ring") pattern as seen in Christian Viladrich's very nice work up on Jacquinot spot issues found here.

 

Solutions: Refine your etalon tuning, probably doing one etalon at a time as possible.* As noted I would first check your optical alignment of both the objective and the focuser as best as possible. Be sure your etalon modules are exactly perpendicular to the optical and mechanical axis. Replace the BF diagonal with a straight through if not already accomplished. Ditch the secondary DS module and double stack with a front mounted etalon. Lastly ditch the whole internal etalon system and go with a front DS system.

 

OR

 

Use your LS100MT system only for close-up work, and get a good 60 mm front DS system for full-disc viewing/imaging.

 

* A Hydrogen spectrum tube would be ideal for this purpose. Then refine the tuning at the scope as needed.


Edited by BYoesle, 26 November 2021 - 01:50 PM.

  • chemman, MalVeauX and lorenzo italy like this

#13 chemman

chemman

    Apollo

  • -----
  • topic starter
  • Posts: 1,142
  • Joined: 21 Jun 2011
  • Loc: Colorado

Posted 26 November 2021 - 11:51 PM

So here is the kit.  This is shot hot off the mount in focus used earlier today.  Currently with a Explore Scientific 3x Focal Extender, ZWO tilt adapter and ZWOASI1600MM.  That configuration concerns me it is not at critical sampling with 3.8um pixels.  ROI'd to 1920X1200 and got 60fps, about 1/2 the 174.  Today had high clouds so not that great.

 

Really at this point trying to digest all of your great comments.  Thanks a lot Bob and Marty, you guys are a huge wealth of knowledge here on this forum.  To be honest I don't really want the pretty pictures I want to capture the science of what we can see on our Sun.  Exactly what is going on over there anyhow?  

 

Really want to have a pressure supply and control for the PTs.  Have not been able to find a Lunt USB-PC controller.  I have been working with Pitot Static systems on aircraft and instrumentation for 25+ years but am hesitant to put it all in on the etalons on the Lunt scope.  Actual pressure in the cavity given I am currently at 8000ASL  and pressures to cavity maximum pressure spook me.  Turning the knobs on the scope to get precise tuning is not my forte and I find somewhat disturbing, visually literally.  Turning a precise pressure regulator knob or tuning via digital computer interface is much more my style.  I actually have the Lunt pistons with hose adapters and hoses but have not incorporated them into the rig.  

 

bvD2NVV.jpg

 

Chuck



#14 MalVeauX

MalVeauX

    Cosmos

  • *****
  • Posts: 9,740
  • Joined: 25 Feb 2016
  • Loc: Florida

Posted 27 November 2021 - 12:11 AM

Hey Chuck,

 

Just to clear up a few things that may matter...

 

A) You're using an F7 scope with a 3x Focal Extender (telecentric type design) and the MN34230 (1600MM) in this configuration? That's F21 and way over-sampling. If this is the case, I would highly suggest you back up to 2x for F14 for a perfect critical sampling match.

 

B) If you have not tried a different barlow, I would advise that you try another more simple barlow. I found a lot of issues with E.S. Focal Extenders in various configurations with solar imaging both in photosphere and other wavelengths. Maybe its anecdotal on my part. But, if you haven't already, I would definitely try a simple barlow optic in its place instead, nothing special, not even a powermate, etc, just a plain old long 2x barlow. Just to be sure nothing weird is going on with that Focal Extender.

 

C) When you reduced the ROI on your MN34230, could you share more about what exposure settings you used? What gain you're having to use and what exposure time you're using? A screen shot of your acquisition software actively recording data would be helpful to see the buffer, the potential max FPS, the actual FPS and any dropped frames occurring?

 

The other thing to keep in mind is that the Lunt 100 with internal etalons (I was under the impression it was externals, confused it with another user that has two external Lunt 100's), the size of those internal etalon(s) and scope objective matters a lot relative to the field and acceptance angles with respect to how it effects the jacquinot spot. It would need to be a pretty big 50mm clear aperture etalon for that. I'm not sure that's the case. It may be nice to email Lunt and ask about the clear aperture size? It would clear up any misconceptions. I only bring this up because the big Lunt scopes (130mm, 150mm etc) have smaller etalons internal to them relative to their objective and do not produce full discs in their jacquinot spot, they are truly partial disc instruments in terms of the view that is going to be in the jacquinot spot. I know for sure the size of the etalon in the Lunt 80 is large enough to keep the jacquinot spot large enough for a full disc. And the front mounted Lunt 100mm etalons can do a full disc in their respective jacquinot spot size. But it may be good to find out what size is in the internal Lunt 102mm to clear this up potentially. But this could potentially have a hand in the puzzle about why you're not getting the full disc in the sweet spot with even illumination; or not! More info there would always be useful.

 

Very best,


  • chemman likes this

#15 chemman

chemman

    Apollo

  • -----
  • topic starter
  • Posts: 1,142
  • Joined: 21 Jun 2011
  • Loc: Colorado

Posted 27 November 2021 - 01:22 AM

As I recall the 80 and the 100 use the same etalons, maybe 35mm?  

 

Not sure.  I would be slightly disappointed if the 100 actually had less capabilities than the 80 though.  

 

I would rather think I simply don't know how to properly operate the instrument.  

 

Chuck

 

Entrance pupil PT Etalon#2 LS100MT

 

ANSPwbV.jpg


Edited by chemman, 27 November 2021 - 01:48 AM.


#16 rigel123

rigel123

    ISS

  • *****
  • Posts: 20,598
  • Joined: 29 Jun 2009
  • Loc: SW Ohio

Posted 27 November 2021 - 07:19 AM

The double stack module for the LS100MT is the same as for the LS80MT.  They make separate DS modules for the LS80T and LS100T.



#17 BYoesle

BYoesle

    Fly Me to the Moon

  • *****
  • Posts: 7,299
  • Joined: 12 Jun 2004
  • Loc: Washington USA

Posted 27 November 2021 - 12:54 PM

Hi Chuck,

 

Thanks for posting your kit layout. It might be that part of your image sweet spot offset may be due to just the large moment-arm and sagging of your camera system and intermediate device coupling. Using a long rigid beam to stabilize the focuser to camera distance similar to an optical bench rail might improve the optical axis alignment. These same issues can arise with the DayStar and Solar Spectrum telecentric filter systems.

 

Hi Warren, Marty, and Chuck,

 

The current LS80MT and LS100MT appear to use the identical primary and secondary (DS) internal etalon systems, focuser, etc. The 80MT would therefore likely have the better Jacquinot spot performance for full-disc imaging. I believe the original LS80THa used a 50 mm primary internal etalon, and it generally had outstanding full-disc contrast performance nearly identical to that of a front etalon.

 

LS80 v 100MT.jpg

 

It appears the original LS100THa may have also used a larger internal primary etalon (60 mm?, and possibly shared with the LS152THa), and it indeed had a different DS module compared to the LS80THa DS module. It appears to have had less field angle magnification, and when double stacked had pretty good full-disc imaging performance - at least when used with a front etalon for double stacking.

 

Again however, this is just speculation on my part, and unfortunately, I can find no actual specifications for these data points. There have been some who state the original LS80THa and LS100THa both used 50 mm primary internal etalons. But others stated the LS100THa used a larger etalon, and Rikki at Lunt specified the LS100THa used a 70 mm - which likely was the etalon substrate diameter, not the actual clear aperture of the etalon itself. She also stated the DS unit also used a 70 mm. Stephen Ramsden stated on Solar Chat that both the internal primary and the secondary DS etalons of the LS100THa were 60 mm.


Edited by BYoesle, 27 November 2021 - 04:00 PM.

  • chemman and torsinadoc like this

#18 MalVeauX

MalVeauX

    Cosmos

  • *****
  • Posts: 9,740
  • Joined: 25 Feb 2016
  • Loc: Florida

Posted 27 November 2021 - 04:23 PM

Heya,

 

From Lunt via email, the internal etalon on the Lunt 152mm is a 52 clear aperture etalon. So it will not do a full disc in the entire jacquinot spot. It's truly meant for partial disc high res views of a small FOV of the disc. And that's their largest internal etalon currently.

 

Very best,



#19 chemman

chemman

    Apollo

  • -----
  • topic starter
  • Posts: 1,142
  • Joined: 21 Jun 2011
  • Loc: Colorado

Posted 27 November 2021 - 04:48 PM

Ok, So this morning I decided to put the scope out using binos.  They are very comfortable to spend long viewing sessions and the goal was precise tuning and chasing the sweet spot.  While I was grinding coffee beans for the session I had an epiphany, the spacer, maybe the spacer I had been using to reduce the focus travel is messing with the image train.  Initially used the binos with a 2" ORJ #2 GPC straight in the focuser came to focus on bright full disk reasonably in tune from the previous session yesterday.  There was a section down the center of the disk not well tuned and adjusting both PTs improved it some but still not so good.  Found an hex wrench and removed the 35mm OTA extension that was positioned between the final etalon and the focuser/BF3400.  Brought the binos back to focus and the image had improved significantly.  Did a little more tuning with what seemed like much better contrast and control.  It all may have been in my head but your eyeballs are in your head you know, lol.  Pulled the binos off and attached the ASI1600MM, as I was making adjustments high level clouds moved in and are still obscuring the sun significantly.

 

I have been imaging so much I think I need more eyepiece time to improve my tuning technique.  Precise focus with the Sesto Senso has be a real challenge but after coming up with a specific focus technique seem to be able to do better than by hand.  I wished I had a similar digital way to tune the PTs.  If I could step through precise pressure levels with both etalons I am sure to get better results.  That would also facilitate being able to do off band studies.  Two USB controlled precise pressure supplies that are compact enough to attach to the scope or dovetail would be very nice. 

 

Bob, Marty and Warren

 

Bob the photos you posted of the LS100 and 80 are single stacked with the 35mm spacer on them, same as my scope the day it arrived.  Soon after I put the double stack module on after the spacer. Internal reflections ensued and a call to Faye helped determine the spacer had to go.  That was the end of the internal reflections and the spacer sat on the work bench for the next 6 months.  I wanted to find out if I could shorten the focus travel so put the 35mm spacer on after the second etalon essentially lengthening the OTA and shortening the distance the focuser had to be racked out.  Removing it may or may not have improved the problem with uneven illumination.  Currently have the scope out with the ASI1600mm on the Baader ORJ #2 GPC waiting for the clouds to part, I don't think they will.  Marty I will try as many different ~2x Barlows as I can find and see visually and with the ASI1600mm if even illumination achieved.  Bob I do have a SmallRig 16"X15mm rail that attaches securely to the back end of the dovetail mount and can reach the camera body with a universal lens support elevation clamp.  I had not used it much since the 2"/T2 extension tubes support the camera weight quite firmly and any movement I try to make by forcing the camera typically shows up as RA and DEC play, but I will use it if necessary. Warren I was wondering if you have a 35mm OTA extension for your scope and how does it come into play for you?  

 

Shot this just before complete obscurity by clouds, shot through clouds.  No processing TIFF from autostakkert, No 35mm OTA extension shot through a 1.8x Baader 2" ORJ GPC.  500 frames 27% AS3!.  

 

get.jpg?insecure

 

- other images from today

Binos   https://i.imgur.com/ANSPwbV.jpg

ASI1600mm https://i.imgur.com/j5Fjskx.jpg

Spacer BF3400   https://i.imgur.com/kuSmRiU.jpg

Front of BF3400   https://i.imgur.com/zkLneRK.jpg


Edited by chemman, 27 November 2021 - 05:04 PM.

  • MalVeauX likes this

#20 MalVeauX

MalVeauX

    Cosmos

  • *****
  • Posts: 9,740
  • Joined: 25 Feb 2016
  • Loc: Florida

Posted 27 November 2021 - 05:21 PM

Hey Chuck,

 

Looks like your have the illumination issue improved. There's some sag somewhere though. Notice the left side of your disc softens up fast compared to the center and right. I can't tell if you're off-band, obviously you're close with clear filaments and all. But the overall look is odd to me, like gamma was used or a heavy increase in mid-tones or shadows? Since you said no processing, I'm assuming you manipulated gamma in Firecapture and recorded it? I would avoid doing that.

 

This is the hardest part of these systems frankly, getting them tweaked... takes forever sometimes :p

 

Very best,


  • chemman likes this

#21 rigel123

rigel123

    ISS

  • *****
  • Posts: 20,598
  • Joined: 29 Jun 2009
  • Loc: SW Ohio

Posted 27 November 2021 - 06:09 PM

I think Chuck has his tuning down from a standpoint of even illumination.  Zooming in I do see that the left side does soften compared to the right.  I am guessing he had Gamma turned on like I suggested to get the best even illumination and simply didn't turn it off since he rarely uses Gamma if at all.

 

Chuck, my system is an internal tilt etalon with a front mounted tilt DS unit as well, no spacers at all.


  • chemman likes this

#22 chemman

chemman

    Apollo

  • -----
  • topic starter
  • Posts: 1,142
  • Joined: 21 Jun 2011
  • Loc: Colorado

Posted 27 November 2021 - 07:03 PM

Hey Chuck,

 

Looks like your have the illumination issue improved. There's some sag somewhere though. Notice the left side of your disc softens up fast compared to the center and right. I can't tell if you're off-band, obviously you're close with clear filaments and all. But the overall look is odd to me, like gamma was used or a heavy increase in mid-tones or shadows? Since you said no processing, I'm assuming you manipulated gamma in Firecapture and recorded it? I would avoid doing that.

 

This is the hardest part of these systems frankly, getting them tweaked... takes forever sometimes tongue2.gif

 

Very best,

I had to go to Sharpcap and look for Gamma, I never use it and could not find it. If I am doing some gamma something I didn't know it and really don't want it.  lol  As soon as I got what looked good and even image in the binos I unscrewed them from the T2 on the Baader GPC and screwed on a T2 extension and the camera, looked up and high clouds and had moved in.  They were there as I shot, I could see the histogram wandering around so what you may be seeing Marty is cloud artifacts.  AS3! seems to handle clouds weird.  

 

Chuck


Edited by chemman, 27 November 2021 - 07:08 PM.

  • rigel123 and MalVeauX like this

#23 chemman

chemman

    Apollo

  • -----
  • topic starter
  • Posts: 1,142
  • Joined: 21 Jun 2011
  • Loc: Colorado

Posted 27 November 2021 - 09:11 PM

Can a Tilt adapter cause a change in the even illumination or focus? 

 

Sure does seem like it would.  When I first brought up the Sun in Sharpcap at 50ms it was totally blown out and had Newtonian ring galore so put a ZWO tilt adapter on the camera mount directly.  Another question: Does it matter where in the image train the tilt adapter is applied?  

 

Marty is there a particular 2x Barlow you would suggest?

 

Chuck


Edited by chemman, 27 November 2021 - 09:12 PM.


#24 MalVeauX

MalVeauX

    Cosmos

  • *****
  • Posts: 9,740
  • Joined: 25 Feb 2016
  • Loc: Florida

Posted 27 November 2021 - 10:14 PM

Can a Tilt adapter cause a change in the even illumination or focus? 

 

Sure does seem like it would.  When I first brought up the Sun in Sharpcap at 50ms it was totally blown out and had Newtonian ring galore so put a ZWO tilt adapter on the camera mount directly.  Another question: Does it matter where in the image train the tilt adapter is applied?  

 

Marty is there a particular 2x Barlow you would suggest?

 

Chuck

Too much tilt will just move things around and cause fringing rings or newtonian rings, but it won't change overall orentation unless the adapter allows some sag. Overall the more in your imaging train, the more flexure and sag there will be. Tiny bits is all it takes, even with a pretty good focuser. People take for granted that solar imaging trains get heavy and long, fast, instead of compact and near the focuser so we suffer from flexure problems often due to this. Some folk build rails to handle the imaging train and stabilize it.

 

The tilt adapter really should be as close to the sensor as possible; it's a weak connection point so you want the least weight on it.

 

No particular barlow I would suggest. If what you have is working, use it. I would just mainly suggesting to make sure and eliminate that particular focal-extender as a source of problems; if it's not a problem, no need to swap it out. The best barlows in general are the long barlows (not the shorties) for simple optics. Your system has no need for telecentric design, but powermates are commonly used, and the focal-extender is E.S. version of what is similar to a powermate (both are advertized as telecentric, but they're not entirely truly telectric at 2x).

 

Very best,



#25 BYoesle

BYoesle

    Fly Me to the Moon

  • *****
  • Posts: 7,299
  • Joined: 12 Jun 2004
  • Loc: Washington USA

Posted 27 November 2021 - 11:52 PM

Looks like your have the illumination issue improved.

I think Chuck has his tuning down from a standpoint of even illumination.

 

Hi Chuck,

 

I'll have to disagree. Your last image is frankly horrible. Your first image is actually much better. While you've centered the Jacquinot spot, it is grossly off-band (not gamma, cloud artifacts, etc.) Only the periphery of the solar disc is on-band, and as noted the left limb is out of focus. If the center was tuned on-band, then the periphery would be equally off-band. As previously noted, you also have an alignment issue or too much tilt applied to the camera.

 

Chuck GONG compare.jpg

Click for larger.

 

On the left I've applied a little bit of LR deconvolution to your image to highlight how far off-band you are in the center. Judging by this image, your Jacquinot spot at best is only about 0.3 degree. On the right is todays similar GONG image to show you what the disc should look like. This severe a not-so-sweet spot would be reason enough for me to contact Lunt with the images and see whether this is what an in-spec LS100MT should provide - something appears amiss to me.

 

While a small Jacquinot spot might be acceptable in a large aperture high-res specialized telescope like the LS152 or 230, it seems inappropriate for what would be a general purpose instrument of 100 mm aperture.

 

You also might want to consider picking up this scope ASAP. It may have a Tucson SM90 DS etalon (inquire about that), and if so that is worth more than half the scope's cost out the gate. Indeed, such an etalon would by itself cost more than the entire package adjusted for inflation.


Edited by BYoesle, 28 November 2021 - 10:07 AM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics