h-alpha, July 11th, 2022

[LTHB]

At the end of a long afternoon of decent to splendid seeing I had too many videos on my hard drive to process everything in one evening. I managed two at least, AR3055 and AR3053.





(Full resolution: https://live.staticflickr.com/65535/522 ... 0546_o.jpg https://live.staticflickr.com/65535/522 ... 4501_o.jpg )

Best regards,

Frank

[ffellah]

Fantastic shots Frank, showing very fine detail. These are lovely !

Franco

[MAURITS]

Indeed fantastic images Frank.

[marktownley]

These look great Frank

[LTHB]

Thanks Franco, Maurits and Mark!

I've processed another couple of videos in the meantime. Imaging is fun when there is so much going on in the chromosphere.







(Full resolution: https://live.staticflickr.com/65535/522 ... 73f5_o.jpg https://live.staticflickr.com/65535/522 ... 96d5_o.jpg https://live.staticflickr.com/65535/522 ... defc_o.jpg )

Best regards,

Frank

[p_zetner]

Superb shots, Frank!
Cheers.
Peter

[Valery]

Nice results, Frank!

Can you, please, include the description of the setup(s) ?


Valery

[arnedanielsen]

Fantastic results, Frank!

Thanks for sharing,
Arne

[LTHB]

Thanks Peter, Valery and Arne!

Valery, the setup for the high resolution is a Mewlon 210 with ARIES D-ERF, 3xTelecentric, Daystar Quantum 0.5A, LS35 etalon, PlayerOne Apollo-M.
For the other images I use a Sky-90 with two old double-stacked Coronado SM90 filters, ASI290 respectively ASI178 (for the disk).

In the meantime I've processed two more shots of AR3055. The first was taken roughly an hour after the image posted above, the second one another hour later, so if one likes one can look for small changes on that time scale.






Finally a disk:



(Full resolution: https://live.staticflickr.com/65535/522 ... cf38_o.jpg https://live.staticflickr.com/65535/522 ... 4464_o.jpg https://live.staticflickr.com/65535/522 ... 20e3_o.jpg )

Best regards,

Frank

[Valery]

Hi Frank,

Your high res images are sharp with a lot of fine details. However, I see that you missed the core of the H-a line.

If this was not done intentionally, then you need to find the best QUANTUM etalon's adjustment position for this given telescope and TZ3 combination. It must work much better. After you will find this best Quantum CWL adjustment, LS35 can be added and then you need to adjust LS35's CWL so, that you will see a uniform contrast and brightness accross the FOV. Always use this Quantum CWL adjustment forr this scope and TZ3.
These two etalons should work really nice and show no double limb.


Valery

[Carbon60]

Lots of wonderful details in these close views, Frank. Nice.

Stu.

[LTHB]

Thanks, Stu!

Valery, thanks a lot for your hints and suggestions for improvement, very much appreciated! I still cannot tell just by looking at the images if they are a bit off-band or not, like you can, but you are surely right.

Three months ago I‘ve spent quite a bit of time trying to tune the Quantum and the LS35 with an h-alpha lamp (like Christian describes on his webpage and in his book). The LS35 should be quite precisely on band now.

The Quantum, however, seems to have a problem: First, judging from the h-alpha lamp measurements, the calibration of its display is way off, but in addition to that I suspect that the Quantum‘s heater is not really working as it should: It sometimes takes a really long time until the green LED signals that it has reached its working temperature, and also it looks to me (sometimes, not always) as if in one corner of the field the band-pass is drifting off.

After some unsuccessful attempts to fix the calibration – see viewtopic.php?t=35397 and
viewtopic.php?t=35913 -
I have come to the conclusion that the Quantum needs to take a trip to Daystar for servicing. I expect this to take a couple of weeks, if not months, so I plan to do that in fall/winter when the weather usually does not allow for any imaging anyway. I don‘t want to miss out on the spectacular things now to be seen on the sun, so I tune the Quantum as good as I can for now and I use it like that over the summer.

Best regards,

Frank

[marktownley]

Sending it back to the menders sounds a sensible idea to me Frank.

[DeepSolar64]

Very nice high-rez work and full discs. Thanks for posting them.

[Valery]

Hi Frank,

The difference in the Quantum native CWL position and the REAL CWL position in a real telecentric setup(s) MUST be different.
All etalons tested at a palallell incoming light. In the telecentric system there is a CONE of the incoming light. So, the etalon works here with it's real CWL being shifted to the blue wing. You need to INCREASE the working etalong temperature to shift the CWL.
The faster the F/D in your telecentric, the higher the working temp should be.
So, use a single stacked (only Quantum) setup and make several images (10-15sec cadence) with increasing temperatures at each next image. The contrast and exposure time must be intact and the scope must be pointed at the center of the sun disk.
If the second image will be darker than the first and the third one is darker than the second, then you on the right way.
Then continue this way untill you will clearly see that the images become brighter. Stop here and write down the temperature value where the image is the darkest. Then go back to the image just prior of the darkest one and to all the same with smaller step of the etalon temperature change. Find the darkest image in this serie and write down the temp value.

When you will compare the images, do not do any image processing! No flats either. Scale down these images 5x or 7x and
compare then at the screen simultaneously. This will make the choosing much easier.

If in the very beginning your second or third image become more bright, then the first one, then the starting point was at too high temperature and you need to start at a lower temperature or go fron it but in the opposite direction - to decreas ethe working temperature.

I hope that this description of the process is clear enough despite my english.

Remember, please, that LS35 will NEVER be correctly adjusted. It's tilt depends of the F/D of your telecentric and also depends of the barometric pressure and air temperature. Some best (for visual, in a front of objective) air spaced etalons, which require a very little to no tilt to be at the H-a core. Telecentric produce light cones F/D where the incoming light is tilted. So, may be a LS35 for double stack is better for your task - to work at about F/40. Barometric pressure and air temp can also require additional tilt.
So, may be your Quantum work well, but the LS35 is out of band (in the blue).

Go with only Quantum, find where it has the best working temp for this given setup (about F/36-37.5) and only then try to add the LS35 etalon and start as follow: Quantum is at it's best temperature you have found and the LS35 is a NO tilt. Then try to tilt the LS35 step by step. Hope the picture will start to improve. If adding LS35 with NO tilt does not makes images much more contrasty vs single Quantum, then try to tilt the LS35. If no improvements seen, then this LS35 is not for working in the telecentric at F/36-37.


Hope this help.


Valery

[marktownley]

Hi Frank,

The difference in the Quantum native CWL position and the REAL CWL position in a real telecentric setup(s) MUST be different.
All etalons tested at a palallell incoming light. In the telecentric system there is a CONE of the incoming light. So, the etalon works here with it's real CWL being shifted to the blue wing. You need to INCREASE the working etalong temperature to shift the CWL.
The faster the F/D in your telecentric, the higher the working temp should be.
So, use a single stacked (only Quantum) setup and make several images (10-15sec cadence) with increasing temperatures at each next image. The contrast and exposure time must be intact and the scope must be pointed at the center of the sun disk.
If the second image will be darker than the first and the third one is darker than the second, then you on the right way.
Then continue this way untill you will clearly see that the images become brighter. Stop here and write down the temperature value where the image is the darkest. Then go back to the image just prior of the darkest one and to all the same with smaller step of the etalon temperature change. Find the darkest image in this serie and write down the temp value.

When you will compare the images, do not do any image processing! No flats either. Scale down these images 5x or 7x and
compare then at the screen simultaneously. This will make the choosing much easier.

If in the very beginning your second or third image become more bright, then the first one, then the starting point was at too high temperature and you need to start at a lower temperature or go fron it but in the opposite direction - to decreas ethe working temperature.

I hope that this description of the process is clear enough despite my english.

Remember, please, that LS35 will NEVER be correctly adjusted. It's tilt depends of the F/D of your telecentric and also depends of the barometric pressure and air temperature. Some best (for visual, in a front of objective) air spaced etalons, which require a very little to no tilt to be at the H-a core. Telecentric produce light cones F/D where the incoming light is tilted. So, may be a LS35 for double stack is better for your task - to work at about F/40. Barometric pressure and air temp can also require additional tilt.
So, may be your Quantum work well, but the LS35 is out of band (in the blue).

Go with only Quantum, find where it has the best working temp for this given setup (about F/36-37.5) and only then try to add the LS35 etalon and start as follow: Quantum is at it's best temperature you have found and the LS35 is a NO tilt. Then try to tilt the LS35 step by step. Hope the picture will start to improve. If adding LS35 with NO tilt does not makes images much more contrasty vs single Quantum, then try to tilt the LS35. If no improvements seen, then this LS35 is not for working in the telecentric at F/36-37.


Hope this help.


Valery

Sage information there. Thanks Valery!

[LTHB]

Thanks for the detailed instructions, Valery! I‘ll try that at the next opportunity. Unfortunately I‘ll need a long stretch of clear blue sky for this, as every change of the Quantum‘s temperature setting takes quite a long time - around 15min until the status LED shows green light again. But hopefully the weather may get better in the next weeks!

My LS35 etalon did at first require quite a lot of tilt to come on band, but I have installed the mechanical pressure tuning mod that Bob Yoesle invented - see viewtopic.php?f=9&t=33217 .
After that I could pressure-tune it with the h-alpha lamp, so that it is on-band without any tilt. So now only moderate tilt of the LS35 is necessary to account for air pressure/temperature changes and the F/D of the telecentric light cone. Tuning the LS35 using the tilt wheel is now quick and easy – the tedious part is the Quantum that takes much time to settle in after every little change of its band-pass.

Thanks again for the great advice, very much appreciated!

Best regards,

Frank

[LTHB]

I have just perused Christian‘s useful website to check if I can estimate how far off band my images probably are. According to one plot there the CẂL shift of a mica-spaced etalon at focal ratio 35 (11.5 for the Mewlon, a factor 3 for the telecentric) should be roughly -0.15A. The central obstruction of the Mewlon should shift it some more towards blue, but I could not find numbers for this effect.

From another plot I took that the LS35‘s CWL should shift -0.3A at focal ratio 35. So I guess the images may be something around 0.3A in the blue wing. In Christian‘s book there are some images (from the Swedish Solar Telescope, p.214) taken in the blue wing of the h-alpha line at -0.8, -0.6 and -0.4A that look to me as if my estimate may be in the right ballpark.

An important point I just noticed is that it was a mistake to „pressure-tune“ the LS35 exactly on band with the h-alpha lamp. In this configuration the CWL shift caused by focal ratio and central obstruction cannot be compensated by tilting the LS35.

So, something for my to-do list…

Best regards,

Frank

[LTHB]

Unexpectedly I could take a few videos this afternoon before the haze thickened too much. Not enough time and conditions not stable enough for systematic tests, but I decided to just try shifting the tuning of the Quantum and the LS35 a bit to the red based on my estimation described above and see what happens.

Only one video of AR13057 was fit for processing, and while the resolution is not that great, it is probably enough to compare it to an image of AR13057 with the old filter settings from Wednesday.





To me this probably looks like a step in the right direction (less conspicuous bright dots in the new image), although I don't know if I've hit the line center now or how close I am (or maybe I am already in the red wing?). I'll look into this more systematically, as Valery recommended, when the weather allows.

Best regards,

Frank

[DeepSolar64]

Frank,
I see 3 or 4 tiny white dots at the edge of the penumbrae of the spots in the last image. They may be ellerman bombs.

JP

[marktownley]

Definitely a step in the right direction Frank!