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Some Sun on a Sunday with Lunt 50mm SS

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#1 WLR_DAD

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Posted 10 December 2023 - 03:10 PM

Fairly new to imaging solar.  This is definitely a different beast than DSO's.  

 

Dec 10, 2023
Seeing: poor
Little Rock, AR
OTA: Lunt 50mm single stack, 6mm block (B600), pressure tuned
Camera: ASI178 MM
Mount: Skywatcher SolarQuest
Controller; laptop using Sharpcap
1000 frames with flats
Stacked/processed: AS!3 (best 25%), ImPPG, PS (inverted/cropped).

 

Does any one know an alternative to a 1.25 feather touch focuser? I would like to upgrade my stock focuser, but the recommended upgrade from Starlight instruments is not available and no lead time.   I've seen some recommend the Moonlight focuser, but this is also unavailable/discontinued.  Thanks

 

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#2 Skywatchr

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Posted 10 December 2023 - 05:08 PM

You can upgrade the helical focuser with a better helical, but you still have a helical. It works and does the job as-is.  My LS40 is the same with the helical. You'd be better off, financially-wise to save up for a double stack Etalon for it. The Sun will "come alive" with more detail.



#3 Highburymark

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Posted 10 December 2023 - 05:09 PM

The Moonlite was popular when the LS50 was launched around 7-8 years ago. Hasn’t been available for many years - indeed, Moonlite no longer makes manual focusers, unfortunately.

#4 BYoesle

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Posted 10 December 2023 - 08:51 PM

Fairly new to imaging solar.  This is definitely a different beast than DSO's.

Indeed.

 

You are also significantly off-band:

 

Image1.jpg

Click for larger.

 

See here for additional information.

 

Start at the basics; forget the fad of negative images and colorization and get some good basic tuning and observing skills down, and then move to imaging. You don't need to stack more than 30 frames, and I question the use of flats unless absolutely necessary. What does your unprocessed image look like?


Edited by BYoesle, 10 December 2023 - 09:06 PM.

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#5 WLR_DAD

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Posted 11 December 2023 - 06:27 AM

Indeed.

 

You are also significantly off-band:

 

attachicon.gif Image1.jpg

Click for larger.

 

See here for additional information.

 

Start at the basics; forget the fad of negative images and colorization and get some good basic tuning and observing skills down, and then move to imaging. You don't need to stack more than 30 frames, and I question the use of flats unless absolutely necessary. What does your unprocessed image look like?

Thanks for the feedback.  You are correct that I have a lot to learn. 

Here is 30 frames straight out of AS!3 

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Edited by WLR_DAD, 11 December 2023 - 06:28 AM.

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#6 Helen P

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Posted 11 December 2023 - 09:07 AM

The Moonlite was popular when the LS50 was launched around 7-8 years ago. Hasn’t been available for many years - indeed, Moonlite no longer makes manual focusers, unfortunately.

There is a feathertouch focuser , specially designed for the Lunt 50... but it is expensive.



#7 BYoesle

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Posted 11 December 2023 - 09:58 AM

Hello WRL DAD,

 

Well it looks by that image that you have an etalon with very good to superb uniformity. If that uniformity is maintained when on-band (and there's no reason it shouldn't), there would be no need for doing a flat. 

 

Nonuniformity in etalon filters is the result of a varying bandpass across the etalon diameter. A flat will fix the resulting brightness variation, but will not correct the variation in detail that accompanies the brightness variation. So using a flat with narrow-band solar images to fix excess brightness variations is essentially "putting lipstick on a pig."

 

Solar narrow-band imaging is almost identical to lunar and planetary "lucky" imaging. But instead you are generally struggling with worse seeing conditions occurring during the day. The goal is to capture the good frames out of a limited duration exposure run. While this may vary, generally for a full disc you would capture for no more than 30 seconds, and stack only as many of the good frames as needed to eliminate any noise. I generally would capture frames for 20 secs, end up with about 350-400 frames, and stack the best 10%. Stacking for longer or more frames only increases the possibility of feature movement, and this becomes more significant at greater image scales.

 

Something that you absolutely have to learn how to do is get on-band. These filters need to be tuned and centered on the H alpha line. This is something you don't even need to address with the broader band nighttime nebula filters. Again, ignore prominences. They are visible at a wide variety of etalon tunings. A more reliable method is getting the filaments as dark as possible, and any plage in active regions as bright as possible. Click on images for larger versions.

 

Etalon tuning sm.jpg

 

Bring the latest GONG H alpha grayscale images to get a good idea of what you should see.

 

Lastly for imaging, I have found under exposure works best so as to not blow out the active regions, and bring out the fainter prominences with processing. Even 8 bit image captures will have sufficient dynamic range to make this more than doable - even with single etalon systems. Double stacking will make it even easier because it removes a considerable amount of photospheric leakage from the disc:

 

Histogram adjustment:

Processing DS images 1sm.jpg

 

Curves:

DS processing 2.jpg

 

Using a single underexposed image (at the far left of the series) to create multiple progressively brightened images to allow an HDR process:

HDR screen.jpg

 

Using just a bit of unsharp masking, wavelets, or deconvolution will generally end the processing:

Full Disc HDR SM.jpg

Double stacked SM90/90/BF30, 6 pane mosaic. ED 100/90, PGR Chameleon, FireCapture, RegiStax6, Paint Shop Pro.

 

Given you have what appears to be an excellent etalon with very uniform band-pass contrast, the aim should be to use as little processing as needed. Once you perfect your tuning skills, you should get excellent results. Consider double stacking with a second etalon as resources allow - you'll be blown away by the difference.

 

Regarding the focuser, there is a huge backorder situation, and it will take you many months to get a Feathertouch of any kind, but especially it seems to have created a bottleneck for the Lunt telescopes.


Edited by BYoesle, 12 December 2023 - 05:24 AM.


#8 BYoesle

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Posted 11 December 2023 - 11:32 AM

For tuning, some might find the collimated light provided by the sun itself a helpful way to fine-tune their etalon.

 

In this series of images below of a SM40 etalon by Christian Viladrich, you can see the variation of the etalon gap which produces changing central wavelengths across the etalon. The bright areas are on-band. The etalon is essentially most on-band in the middle where the variations are the most balanced around 656.28 nm. This therefore is a good way to both tune an etalon, and to judge etalon quality:

 

SM40 collimated tuning C Viladrich.jpg

 

With regard to negative disc images, this is a cheat to hide the double limb produced by single etalon systems. IMHO this makes the sun's disc about as attractive as a petri dish filled with bacteria, and a complete misrepresentation of a heavenly body.

 

Sophia.jpg

 

So if I'm going to use a negative image, I'll keep the disc a positive and negativize the prominences. This actually works better for visual discrimination, as our perception is better for dark features on a light background:

 

gallery_3892_8222_116962.jpg

 

This also more clearly connects prominences and filaments as being the exact same phenomena.

 

YMMV



#9 WLR_DAD

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Posted 17 December 2023 - 09:32 AM

For tuning, some might find the collimated light provided by the sun itself a helpful way to fine-tune their etalon.

 

In this series of images below of a SM40 etalon by Christian Viladrich, you can see the variation of the etalon gap which produces changing central wavelengths across the etalon. The bright areas are on-band. The etalon is essentially most on-band in the middle where the variations are the most balanced around 656.28 nm. This therefore is a good way to both tune an etalon, and to judge etalon quality:

 

attachicon.gif SM40 collimated tuning C Viladrich.jpg

 

With regard to negative disc images, this is a cheat to hide the double limb produced by single etalon systems. IMHO this makes the sun's disc about as attractive as a petri dish filled with bacteria, and a complete misrepresentation of a heavenly body.

 

attachicon.gif Sophia.jpg

 

So if I'm going to use a negative image, I'll keep the disc a positive and negativize the prominences. This actually works better for visual discrimination, as our perception is better for dark features on a light background:

 

attachicon.gif gallery_3892_8222_116962.jpg

 

This also more clearly connects prominences and filaments as being the exact same phenomena.

 

YMMV

Thanks Bob for your wisdom and explanation.  Today looks promising for solar imaging and I will work on my tuning.  I saw on a YT video that suggested using the historgram as a tool for tuning.  It suggested adjusting the tune pressure by watching the histogram and as it moves furtherest to the left, you be "on-band".   Any merit to this method?  Thanks



#10 BYoesle

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Posted 17 December 2023 - 05:43 PM

I haven't used it, and when used for focusing the histogram is not as good as my eyeball. If you have a visual difficulty it might be appropriate.

 

I always use visual appearance for focusing and tuning, and the collimated method for fine tuning. 




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