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#7301 neaptide

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Posted 28 January 2019 - 12:02 PM

It is kind of funny. Amateurs say you can double stack two F/.63 reducers atop one another to achieve F/3.7 Focal ratio. I tried that a few times, it produces a lot of vignetting on the outer 1/4 of the FOV. I only use that when I want magnified images at F/3.7 with my Nexstar C8. I also can get  F/3.78 with my AT60ED, native F/6, using one Meade F/.63 focal reducer on my little APO refractor and it produces a nice 4.4 degree x 3.84 degree FOV.

Not sure what other folks tolerance for vignetting is or what F ratio they were achieving but I do recall a few folks being very happy with their double stacked .63 reducers. I never tried it because my configuration @ F/3.7 worked so well without any appreciable vignetting .


Edited by neaptide, 28 January 2019 - 12:37 PM.


#7302 saguaro

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Posted 28 January 2019 - 12:08 PM

Use an IR/UV block filter to reduce the star bloat. Works very well!

Yes, thanks David, that is true. But since galaxies emit in IR, I didn't want to use a UV/IR block. The CLS filter I used (not the CCD version) allows IR to pass. Since I can't easily switch filters during a session, and I was going to be looking at both galaxies and nebula, I thought the CLS might be a good compromise. But for my outreach purposes, I determined that no filter is the best option, since I can use lower gain and still maintain 15sec exposures or less, and the public doesn't care if the stars look bloated smile.gif .

 

However, I think next time I will try my UV/IR cut filter to see whether I prefer it vs. no filter.


Edited by saguaro, 28 January 2019 - 12:48 PM.


#7303 Stargazer3236

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Posted 29 January 2019 - 07:43 AM

Not sure what other folks tolerance for vignetting is or what F ratio they were achieving but I do recall a few folks being very happy with their double stacked .63 reducers. I never tried it because my configuration @ F/3.7 worked so well without any appreciable vignetting .

What configuration are you using now, to obtain F/3.7?



#7304 Stargazer3236

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Posted 29 January 2019 - 07:49 AM

Yes, thanks David, that is true. But since galaxies emit in IR, I didn't want to use a UV/IR block. The CLS filter I used (not the CCD version) allows IR to pass. Since I can't easily switch filters during a session, and I was going to be looking at both galaxies and nebula, I thought the CLS might be a good compromise. But for my outreach purposes, I determined that no filter is the best option, since I can use lower gain and still maintain 15sec exposures or less, and the public doesn't care if the stars look bloated smile.gif .

 

However, I think next time I will try my UV/IR cut filter to see whether I prefer it vs. no filter.

Optolong sells a nighttime H-a filter that passes IR from 650nm and above. It is not the kind to be used for H-a Solar viewing, nor is it the one for H-a nebula viewing. Just a straight up H-a to let the IR bandpass through.

 

When I image, if nebula ( which is most of the time), I use my 2" UHC and the 2" UV/IR block filter to reduce star bloat and enhance my nebula output. When I do galaxies, it is no filter at all.

 

Which CLS filter are you using, what is the brand name?


Edited by Stargazer3236, 29 January 2019 - 07:50 AM.


#7305 neaptide

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Posted 29 January 2019 - 08:42 AM

What configuration are you using now, to obtain F/3.7?

Hey David

 

When I had my C8 I used to put the F/6.3 sct reducer on the scope then I would screw a 2" .5x reducer on to a 2 " nosepiece. I would then put a 10mm t thread spacer onto the camera and screw the nose piece on to that. I used a Baadder SCT quick lock to attach the camera (ASI224) and nosepiece to the scope. I had to spend a rare clear night trying out different spacers to the camera and different configurations until I was happy with my results. 

 

Smaller t thread spacers to the camera would increase F ratio. Larger spacers would lower the F ratio but introduce more vignetting. If I remember right the 10mm spacer was the sweet spot for my set up. Others may have to experiment a little due to differences in the 2" nose piece and if they are using a Baadder quick lock or not.  I think using 2" accessories is necessary for reducing vignetting. 

 

I would upload my Images to astrometry.net then take the info from that and put the numbers into a focal reduction calculator to find what my F ratio was. I can provide links when I get home this evening if you would like. 

 

Cheers

John


Edited by neaptide, 29 January 2019 - 08:50 AM.


#7306 saguaro

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Posted 29 January 2019 - 10:44 AM


 

Which CLS filter are you using, what is the brand name?

I use the Astronomik CLS filter (not the CCD version), which allows IR to pass.


 



#7307 wargrafix

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Posted 30 January 2019 - 12:32 PM

Wow, those histogram settings work wonders!

 

Here is the M51 from a while back

med_gallery_218407_321_195060.jpg

 

here is 5 mins from this morning with those settings

med_gallery_218407_321_109358.jpg

 

Just for fun here are 467 frames at 7472 seconds

 

med_gallery_218407_321_190605.jpg


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#7308 wargrafix

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Posted 30 January 2019 - 12:36 PM

Here is NGC3344. Such a gorgeous spiral galaxy

I fell asleep and forgot to save my 5 min stack.

 

Here is a stack of 544 frames at 8704 seconds

 

med_gallery_218407_321_119061.jpg


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#7309 GoFish

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Posted 30 January 2019 - 09:47 PM

Here is NGC3344. Such a gorgeous spiral galaxy

I fell asleep and forgot to save my 5 min stack.

 

 

lol.gif



#7310 cshine

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Posted 31 January 2019 - 06:13 PM

Wow, those histogram settings work wonders!

 

Very nice! Can you provide a little more detail on what you changed in your histogram settings to get that improvement? Also, do you tend to tweak both the stacking histogram and the Display histogram? I only recently discovered the difference that the Display histogram makes to the stacked image..

Thanks


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#7311 wargrafix

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Posted 02 February 2019 - 09:26 AM

I have a few captures to ujpload. M83 is back and thats a signal that spring is around the corner. I did a 5 minuites and a 5k seconds capture.

This once after 5 minuites looks like a GALAXY.

 

c9.25

 

23 frames @368 seconds

 

med_gallery_218407_321_352877.jpg

 

5040 seconds 315 frames

 

med_gallery_218407_321_244068.jpg

 

Here is a stretch of the 5k seconds data

 

https://www.cloudyni...ames-5040s-m83/


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#7312 Stargazer3236

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Posted 02 February 2019 - 11:17 AM

Hey David

 

When I had my C8 I used to put the F/6.3 sct reducer on the scope then I would screw a 2" .5x reducer on to a 2 " nosepiece. I would then put a 10mm t thread spacer onto the camera and screw the nose piece on to that. I used a Baadder SCT quick lock to attach the camera (ASI224) and nosepiece to the scope. I had to spend a rare clear night trying out different spacers to the camera and different configurations until I was happy with my results. 

 

Smaller t thread spacers to the camera would increase F ratio. Larger spacers would lower the F ratio but introduce more vignetting. If I remember right the 10mm spacer was the sweet spot for my set up. Others may have to experiment a little due to differences in the 2" nose piece and if they are using a Baadder quick lock or not.  I think using 2" accessories is necessary for reducing vignetting. 

 

I would upload my Images to astrometry.net then take the info from that and put the numbers into a focal reduction calculator to find what my F ratio was. I can provide links when I get home this evening if you would like. 

 

Cheers

John

I have bought everything except the Baader Quick lock. I will be getting that next. I am going to try this out with my ASI294MC for now and see what results I get.


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#7313 neaptide

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Posted 02 February 2019 - 01:25 PM

I have bought everything except the Baader Quick lock. I will be getting that next. I am going to try this out with my ASI294MC for now and see what results I get.

Hey David

 

The ASI294 has a significantly larger chip then the ASI224 or the ASI385 so you may not be able to reduce all the way down to F/3.7 without vignetting. In any case the Baader quick lock is a very nice piece of equipment and a little experimenting with the spacing should give you a nice amount of reduction. Looking forward to seeing your results. 

 

John



#7314 FrankG

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Posted 03 February 2019 - 10:04 AM

Am using a ASI294 Pro on my 15" dob. Happy with the results, but aside from being able to use the histogram to improve the image, more stacks really do not improve it - make it brighter, more vivid. It really does not look a lot better at 80 seconds than 20. Is that what I should expect? You can see my settings here. If anyone spots something I'm doing wrong or failing to do please holler.

 

Many Thanks,

 

FrankFeb2100secopy.jpg


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#7315 Stargazer3236

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Posted 03 February 2019 - 10:10 AM

Am using a ASI294 Pro on my 15" dob. Happy with the results, but aside from being able to use the histogram to improve the image, more stacks really do not improve it - make it brighter, more vivid. It really does not look a lot better at 80 seconds than 20. Is that what I should expect? You can see my settings here. If anyone spots something I'm doing wrong or failing to do please holler.

 

Many Thanks,

 

Frankattachicon.gif Feb2100secopy.jpg

Try lowering the gain to about 350. Play around with the color saturation slider to the far right of the Histogram. Increase exposure time with the lower gain, that might improve things. Use the black level slider and just touch the Lum peak in the histogram. Use the mid level and white level sliders more and slide the mid level closer to the white level and then increase the white level towards the black level.


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#7316 neaptide

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Posted 03 February 2019 - 11:01 AM

Am using a ASI294 Pro on my 15" dob. Happy with the results, but aside from being able to use the histogram to improve the image, more stacks really do not improve it - make it brighter, more vivid. It really does not look a lot better at 80 seconds than 20. Is that what I should expect? You can see my settings here. If anyone spots something I'm doing wrong or failing to do please holler.

 

Many Thanks,

 

Frankattachicon.gif Feb2100secopy.jpg

On very bright targets you will not see much of an improvement with very long integration times but you should be seeing some improvement between 20 seconds and 2 minutes. Even on dimmer targets I don't go over 10 minutes because of diminishing returns. Using the livestack histogram is essential in teasing out details and I don't usually try to stretch any image until at least a minute has gone by. 15 second exposures at Gain of 300-400, depending on the target and my sky conditions, work for me.

 

On the histogram bringing the White point over to the left too far will blow out the brightest parts of your image and I like to put the black point around where the peaks of the histogram are.Then I adjust the mid point until I am happy with the image. As the image builds you will see that these adjustments will need to be changed somewhat.

 

I also find that using the automatic color balance really helps bring out details. Click the lightning bolt under the color sliders then make small adjustments to the sliders. The saturation slider on the far right of the color sliders works really well to bring out color and detail.

 

 

Screen shot Orion.jpg


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#7317 saguaro

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Posted 03 February 2019 - 11:43 AM

Am using a ASI294 Pro on my 15" dob. Happy with the results, but aside from being able to use the histogram to improve the image, more stacks really do not improve it - make it brighter, more vivid. It really does not look a lot better at 80 seconds than 20. Is that what I should expect? You can see my settings here. If anyone spots something I'm doing wrong or failing to do please holler.

 

Many Thanks,

 

Frankattachicon.gif Feb2100secopy.jpg

Hi Frank,

 

In your screenshot you are using Brightness 28. I used a friend's 294MC recently and got some good tips from Donboy on this forum to use Gain 300 and set Brightness to either 0, 5, or 10 but not higher since apparently this camera does better with a lower Brightness setting.


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#7318 39.1N84.5W

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Posted 03 February 2019 - 06:47 PM

Avoided the polar vortex and spent time in Tuscon. First light with my new asi294c and Saguaro's 14" SCT, Hyperstar setup. Gain 300, idas p2, 96x8s, cooled to -10c, master dark applied, no flats, no post processing.

Attached Thumbnails

  • rps20190203_164536_429.jpg

Edited by 39.1N84.5W, 03 February 2019 - 06:48 PM.

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#7319 Rickster

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Posted 04 February 2019 - 04:03 PM

That 14" hyperstar/294 is a dynamite combination. I would be switching to that if I wasn't already so far down the another road.
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#7320 saguaro

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Posted 08 February 2019 - 09:25 AM

Recently discovered supernova 2019np in NGC3254 (Leo Minor) is of Type Ia. I observed it last night using SharpCap Pro 3.2 live stacking with master dark. Only cropped, converted to JPG and annotated.

 

You can clearly see the blue color of the SN, which is characteristic of it's measured spectra which shows a peak at around 4K - 5K angstroms. More info is here: http://www.rochester...9/sn2019np.html

 

Supernova 2019np in NGC3254, 15x15sec, 8-inch SCT operating at F/4 using a Meade 3.3 focal reducer, with an ASI385MC camera

 

NGC3254 SN 2019NP 15x15sec.jpg


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#7321 saguaro

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Posted 08 February 2019 - 10:16 AM

A few views from last night using my Evolution Alt-Az mount with an 8-inch SCT operating at F/4 using a Meade 3.3 focal reducer, with an ASI385MC camera (no filters). SharpCap Pro 3.2 live stacking with master dark.

 

Little Dumbell Nebula, 20x15sec

 

little-dumbell 20x15sec.jpg


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#7322 saguaro

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Posted 08 February 2019 - 10:18 AM

Evolution Alt-Az mount with an 8-inch SCT operating at F/4 using a Meade 3.3 focal reducer, with an ASI385MC camera (no filters). SharpCap Pro 3.2 live stacking with master dark.

 

M109, 28x15sec

 

m-109-28x15sec.jpg


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#7323 saguaro

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Posted 08 February 2019 - 10:18 AM

Evolution Alt-Az mount with an 8-inch SCT operating at F/4 using a Meade 3.3 focal reducer, with an ASI385MC camera (no filters). SharpCap Pro 3.2 live stacking with master dark.

 

Running Man, 31x15sec

 

running-man-31x15sec.jpg


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#7324 wargrafix

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Posted 09 February 2019 - 08:42 AM

Nice!!! Do you make fresh darks every session?

#7325 saguaro

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Posted 09 February 2019 - 09:19 AM

Nice!!! Do you make fresh darks every session?

Thanks! Yes, it’s easy to create a new master dark each session since I know by now that 15sec exposures at Gain 300 Brightness 140 will generally work for most targets. The only variable is sensor temp which can vary a lot with our nighttime conditions, so that’s why I find it best to start with a new master dark each session. Re-using a master dark is also possible if nighttime temps are similar. There is still some amp glow, which ZWO told me is more noticeable in winter months when I asked about it here:

https://bbs.astronom...opic.php?t=9725


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