AR2737 High Res in HA & WL & Full Disc in HA | April 3rd 2019

[MalVeauX]

Heya,

I didn't expect much this morning due to forecast, and instead, I was met with rather good seeing. This is the first time I've been able to utilize the full 200mm of my system without it being a fuzzy mess, although I undersampled the HA data. Still not quite perfect, but seeing was flashing 4/5 pretty often and I was able to get some data in two wavelengths on our interesting little AR2737 in HA & WL.





















Equipment:

C8 Edge HD + 0.7x focal reducer + Aires 200mm Tri-Band D-ERF + Baader UV/IR Block Filter
ST80 (masked to 60mm)
Daystar Quark Chromosphere
ASI174MM + 0.5x Focal Reducer
Baader ND 1.8 + Baader 610nm Long Pass + 3x Barlow for the White Light (used with the Aires D-ERF)

solarsetup_04032019.jpg (63.54 KiB) Viewed 1732 times

Very best,

[marktownley]

Lovely images Marty! You can see in those images you're getting the resolution capabilities of that 8" scope, it's very rare I can get seeing to do that. Hope you get more conditions like that.

[ffellah]

Great close-ups of 2737, Marty ! You can tell that the seeing has improved a lot...

Franco

[MAURITS]

Great images Marty.

[MalVeauX]

Thanks, yes, not quite resolving at the full potential, but the seeing was an improvement today over the past 3 months where I was able to finally rival my 150mm refractor for the first time I think. My summer seeing may be better, so I'm hoping for more opportunities to image at the full scale. In this case, for the HA, I'm under-sampled significantly. I usually stop it down to 150mm F9.3 with a mask under the D-ERF for when seeing is not great, and then use the 0.7x Edge reducer, (1400mm focal length, F9.3 with the 150mm aperture). This gives me F39 through the Quark which is great for bandpass and contrast, then I focal reduce it to F19.5 which is a good place to be on the IMX174 pixels. For the above images, I took the mask out and used the full 200mm aperture with the 0.7x Edge reducer (1400mm F7), which was F29 through the Quark's etalon, which is good, but then I reduced it with the 0.5x on the camera to F15, which is not ideal for the IMX174 pixel size at this wavelength, but it's still better than what I've been able to record lately, undersampled, but I'll take it!

For the white light, I used the same tri-band D-ERF at the full 200mm aperture, it passes 656nm of course, so for the white light I used a 610nm long pass filter in addition to the D-ERF to further narrow it down and calm the seeing, and then cut transmission with a Baader 1.8 ND filter. For scale, I used a 3x barlow (since the scope was configured for 200mm at F7 with the focal reducer) to get me back to F21 which is a good focal-ratio for the 656nm wavelength on the IMX174 pixel size to record the resolution, so the convection cells are at a good imaging scale and I cannot improve that without better seeing and then switching to a shorter wavelength (like 395nm, which I have, but rarely the seeing supports that wavelength at this aperture).

Very best,

[marktownley]

A bit of undersampling is not a bad thing when conditions aren't perfect, I agree.

Out of curiosity Marty, do you know if you're 0.5x reducer is actually giving you 0.5x reduction? the factor varies with distance to the chip. Have you done a comparison? take a shot with no reducer, take same shot with reducer and then compare the linear pixel distance between 2 identical points on both images to work out the reduction factor?

[MalVeauX]

A bit of undersampling is not a bad thing when conditions aren't perfect, I agree.

Out of curiosity Marty, do you know if you're 0.5x reducer is actually giving you 0.5x reduction? the factor varies with distance to the chip. Have you done a comparison? take a shot with no reducer, take same shot with reducer and then compare the linear pixel distance between 2 identical points on both images to work out the reduction factor?

I have done a comparison and it's pretty much 0.5x reduction. It's spaced away from the sensor to that effect. I compared it to my C8 Edge (no Edge reducer) at F10 with a 2x barlow (F20) imaging in white light the past AR spot series (2736, etc), and my C8 Edge (no Edge reducer) at F10 with a Quark (F42) with a 2" 0.5x focal reducer spaced 12mm from the sensor plus a little adapter ring to mount it and the thickness and size of the 2" reducer itself, resulting in the same FOV on the spot with the same sensor (IMX174), so it was F21. So it's very close to 0.5x at this placement.

Here's the comparison on the same scope & sensor.

HA is C8 Edge + Quark + 0.5x focal reducer (F21) on IMX174
WL is C8 Edge + 610nm Filters + 2x Barlow (F20) on IMX174



Here's the 2" focal reducer, adapter ring, 12mm 2" spacer on the IMX174:

HighRes_FocalReducer_12mmExtension.jpg (34.49 KiB) Viewed 1687 times

Here's my white light setup (the standard 1.25" nose, Baader 1.8 ND & Baader 610nm):

Solarsetup_03222019_04_StackedFiltersWhiteLight610.jpg (31.66 KiB) Viewed 1687 times

Very best,

[Valery]

My congratulations with starting of a high res imaging season, Marty.

I would give you an advice, if I may. Do not use any HD reducers in a front of Quark. There should be no any additional optics like reducers in front of Quark. You always will get un-aberrated images and stable F/43 cone at the etalon. F/43 will allow you to get significantly narrower bandwidth and significantly more uniform CWL uniformity. You always can regulate the image scale by varying the space between the 0,5x reducer and the camera chip. Just make 2-3 different spacers - the shortest for highest resolution, a bit longer for medium scale and the longest for prominences imaging even if the corners on the chip will not be illuminated (then use the ROI to cut these unwanted vignetted corners.

Why no optics should be between the C8HD and the Quark? All these focal reducers which work at F/10 and give about F/7 are severely suffer from spherical aberration and this makes images much less sharp vs un-reduced. Also, less light scattering and reflections.

You also always can downsize images when post process them - this increases the S/N and the sharpness.

Important note: at F/43 on the Quark etalon, you need to change the best position of the tuning knob to 1 or 2 clicks counterclockwise vs the best position at typical F/30.

Hope that a bit of my experience will help you to reach better final results.


BTW. do you plan to get the SSM ?


Valery

[MapleRidge]

Hi Marty...

These are excellent images from today's session...well done

Brian

[marktownley]

Thanks for the clarification Marty. I need to explore the use of a reducer more in my setup, I use the Baader Telecompressor at around 0.7x reduction factor but found if I go lower than this in terms of reduction I just get too much vignetting. Maybe different if I try a o.5x reducer instead.

At the back end of last years solar season I began experimenting with the edge HD 0.7x focal reducer and my Quark on my HaT, initial results showed it really worked for me, but then again i'm double stacking with the PST etalon too so bandwidth is still tight, and my quark has tight bandwidth anyway. I just need conditions to improve this year so I can carry on with the experiments I started last August.

[MalVeauX]

Thanks,

@Valery, thanks for that, I was using the 0.7x reducer to combat poor seeing and reduce the scale. I'll go back to full scale and play with the reducer on the camera side some more. I do plan on finishing my SSM. I have enough parts to build two of them from scratch, I just need to get around to doing it. I realize I need it more than ever now for sure.

@Mark, I would love to figure out a PST double stack setup at the back of this C8, but I'm not sure if I can achieve focus with the 105mm backfocus of the Edge.

Very best,