120 replies to this topic

[ASTROTRUCK]

" adjusted gain and exposure to create an even histogram "

 

quote from bag flat image above # 72 saguaro

 

what is an even histogram & what does it look like ?

 

will try your bag flat but not sure of the even histogram issue

 

thanks

[saguaro]

" adjusted gain and exposure to create an even histogram "

 

quote from bag flat image above # 72 saguaro

 

what is an even histogram & what does it look like ?

 

will try your bag flat but not sure of the even histogram issue

 

thanks

With your bag in place, adjust the histogram by adjusting gain and exposure so that the peak of the histogram is in the same position along the horizontal axis as when you imaged the disk. The histogram should look like a hill with equally sloping sides. The goal is to get even illumination across the field of view. Hope this helps.

[ASTROTRUCK]

OK THANKS

[ASTROTRUCK]

if the bag image is too bright then reducing the exposure will i expect defeat the purpose of the  flat even if it brings the flat histogram level to that of the image  histogram.

correct ?

[saguaro]

if the bag image is too bright then reducing the exposure will i expect defeat the purpose of the  flat even if it brings the flat histogram level to that of the image  histogram.

correct ?

Not really. For a good result, you want the master flat image to be diffuse and have even illumination across the field of view. You may have to experiment a bit with different plastic bags until you find one that diffuses the image evenly across the field and shows 60-80% on the histogram in FireCapture by adjusting exposure and gain settings.

 

I use a bag flat only for my full-disk images, where the disk doesn't fill the entire field of view. If the image fills the entire view (such as with a barlow), then you may want to try cling film (Saran wrap, etc.) instead of a bag.

 

It's very important to take the bag flat immediately after taking your disk images, so that the disk is in the same place in the frame. If you change anything (rotate the camera, switch to a barlow, etc.) then you will need to take a new flat to match the new imaging setup. Hope this helps.

[ASTROTRUCK]

THANKS

[ASTROTRUCK]

is it worth defocusing infocus before placing the bag ?

 

my images are somewhat uneven so wish to use flats but i am not sure of the procedure.

 

your posts have helped greatly

thanks

Edited by ASTROTRUCK, 21 May 2015 - 10:03 AM.

[saguaro]

is it worth defocusing infocus before placing the bag ?

 

my images are somewhat uneven so wish to use flats but i am not sure of the procedure.

 

your posts have helped greatly

thanks

One of the main advantages of the bag flat is that you do NOT have to defocus the image, thus you do not have to run the risk of the image moving in the frame as a result of touching the scope to defocus the image.

 

It's always best to try to tune the image (by adjusting pressure tuning or tilt) as best you can to help minimize uneven illumination. The bag flat can help with removing any uneven illumination that tuning does not allow you to do.

[ASTROTRUCK]

not sure how to place the bag without shifting the image a small amount even by shaking the scope itself ,,,

 

your image of the flat shows minimal circular disk almost no space around the blurred solar image suggesting the whole frame can be solid opaque so if the image shifts so what as the flat would be solid opaque across the entire field with no disk so what if it moves. - that solid gray of the flat across the field is all that counts  - no ?

 

instead of worrying about it moving - if i repoint the scope with filter & bag  to a point in the clear blue sky using the bag for the flat is that not good also? still all i get is a flat opaque image -  no disk- which is what i want ?

then i can use it for all the full disk images ??

the flat when stacking should have no distinguishing markings correct  so the stacking process with the flat does not use tracking points so a nice clear sky as flat should be good ??

 

what am i missing ?

 

also can i use a solid white garbage bag or is it too solid ?

Edited by ASTROTRUCK, 21 May 2015 - 11:53 AM.

[saguaro]

I've described what works best for me, based on my bag flat tests and trials (using different bags and FireCapture histogram settings) with my particular scope and camera. I'd suggest trying different approaches (like you've suggested) in order to find what works best for your setup and needs.

[Andre444]

hi, i like to know witch is the better choice: " double stacked PST" or the lunt 60 tha tilt tune 600BF Crawford focuser . ( i Will do mainly visual use and if i go for the lunt i never buy a double stack) thanks!!

[bill1234]

Aperture rules. Huge improvement in resolution with the 60. With solar activity waning, edge detail will show the most interesting detail (proms) and the 60 will blow away the 40.  

[BinoGuy]

Help me understand,  Apeture is used for light gathering while the eyepiece provides magnification.  I am under the impression that aperture (light gathering) isn't as much of a necessity for solar viewing/imaging since we are rejecting all but 0.0001% (I think).  Is it because the edge detail is already much fainter than the disk so every little bit of extra light helps, which is why a 60 > 50 > 40?

[bandazar]

I think the magic aperture to start seeing spicules easy is somewhere around 5" to 5.5" from what I've seen.  Yes, you can see them in lower apertures, but it is just harder. 

[Andre444]

Thanks! I Will go for the lunt 60!

Edited by Andre444, 22 July 2017 - 04:04 PM.

[Live_Steam_Mad]

The LS50THa is a high quality instrument. The build quality is just like the LS60 and larger scopes. The view is bright with exceptional detail. Proms are easy and clear to see. Surface detail appears like the skin of an orange. When double stacked the filaments crack across the sun's disk and are easy to see. The back ground is nice and dark, not a lot of red glow. The scope even shows a nice thin line of spicuals which is normally seen in larger scopes. The scope is a winner in my book. I think this will become the new standard for a intro into H-alpha.

Yep I just had First Light with my brand new LS50 / B600 PT Single Stacked (new old stock from 2015 it seems), the view matches your description visually. In addition I even I saw dark filaments in single stack.

 

Regards,

 

Alistair G.

Edited by Live_Steam_Mad, 12 August 2017 - 04:33 PM.

[Live_Steam_Mad]

BTW my stock focuser of my LS50 seems to have 20mm of travel according to the scale?

 

Regards,

AG

[Live_Steam_Mad]

I just measured my LS50 and the minimum spacing between the Etalon and the diagonal is 63.3mm and the maximum is 74.7mm, so the focuser travel is 11.4mm with the stock non-rotating helical focuser! Despite the scale on this focuser showing "20" travel in total, whatever "20" is supposed to mean...

 

Regards,

AG

Edited by Live_Steam_Mad, 14 August 2017 - 09:26 AM.

[Live_Steam_Mad]

Hello Dennis,

 

Congratulations! You will have alot of fun with this scope. You may already have a 1.25-inch nosepiece for your DSLR, but you may not be able to achieve focus using the nosepiece due to the short back-focus of the scope. I'm actually trying to find out from Lunt right now what the back-focus distance is to see if I can match a binoviewer such as the Baader Maxbright with a glass path compensator (GPC) to the scope.

 

With my Skyris 132m, I am able to achieve focus by unscrewing the eyepiece barrel from the front of the blocking diagonal, and then using the Starizona T-to-C adapter to mate the camera's C-threads to the blocking diagonal's T-threads. You may just need a T-ring for your DSLR that will screw into the T-threads on the blocking filter.

 

I've found that I can capture the disk details and the prominences together with the double-stack module (no need to composite the disk with the proms later in photo editing software such as Photoshop). This shot was taken at prime focus (no barlow). I just cropped the image to show half the disk instead of the full disk.

 

 

proms-on-west-limb_-for-web.jpg

 

I've also successfully used a 1.5x barlow:

 

video-8-barlow-final-for-web reduced 50 percent_web.jpg

 

Also, here is a link to my image gallery on Astrobin: http://www.astrobin....robinandcurtis/

 

-Robin

Incredible image Robin!

 

Did you have any Newton Rings in your images with Skyris 132m and your Lunt 50 camera and 'scope combo (and either single stacked or double stacked) that you had to remove with image processing, or did you have no problems with Newton Rings?

 

And BTW which brand & model of 1.5x Barlow did you use for the close up image?

 

Best Regards,

Alistair G.

Edited by Live_Steam_Mad, 23 June 2019 - 12:29 PM.

[saguaro]

Incredible image Robin!

 

Did you have any Newton Rings in your images with Skyris 132m and your Lunt 50 camera and 'scope combo (and either single stacked or double stacked) that you had to remove with image processing, or did you have no problems with Newton Rings?

 

And BTW which brand & model of 1.5x Barlow did you use for the close up image?

 

Best Regards,

Alistair G.

 

Thanks! No problems with Newtons rings with the Skyris 132m. I used a GSO shorty barlow with just the barlow lens element screwed into the 1.25 inch nosepiece that came with the camera. I then insert the nosepiece into the eyepiece holder on the blocking diagonal. The barlow moves the focus point further out so no problem reaching focus when the barlow is used. https://agenaastro.c...arlow-lens.html

[JeromeL_FR06]

Hello Robin,

 

Your images decided me to go with the 50/600, thank you!

I have also a C14 with some ZWO cameras.

Mounted into a G11.

I would like to have some tips from you please.
You said during the thread:
1. I would like to learn how to capture the prominences on the limb - any advice?
2. I still need to figure out how to bring out the prominence detail without somewhat of a "halo" effect on the limb.
3. I'm not completely happy with the tuning in the above image, and I hope to improve on the above results. Any advice or comments?

Are you able to share some tips?

I am facing to exactly the same  now.

If you have already answered and I have missed or don't understand it, I am very sorry.

 

Many thanks!!!

 

Again, your images are amazing!

Be safe,
Jerome

Edited by JeromeL_FR06, 22 May 2020 - 01:57 AM.