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Astrophotography and Sketching >> Beginning and Intermediate Imaging

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JJK
Carpal Tunnel


Reged: 04/28/08

First-light test of FLI ML8300 & 3 nm Astrodon H-a
      #6250079 - 12/12/13 11:08 PM Attachment (22 downloads)

My friend, Joshua Balsam, and I are testing my new monochrome FLI 8300 (w/the Anti Dew Technology option)/CFW2-7 filter wheel, and a set of Astrodon filters (LRGB Gen 2 & 3 nm OIII, H-alpha, and SII narrowband filters. The weather here has been miserable for so long, but we thankfully got a break several nights ago.

The FLI camera cools very quickly, and stays put at the desired point set in MaximDL. The filter wheel is reasonably quiet (more so than SBIG STF- and STT 8300-based cameras I've played with; they're nice but relatively noisy units). The downloads at 8 MHz are very fast (I was used to an STL-11K w/26 second downloads).

Our first-light target with the 3 nm Astrodon H-alpha filter was The Flame/Horsehead region, with the Moon at nearly first quarter phase. We used an A-P 105 mm f/5.9 Traveler with an A-P prime focus field flattener. Josh made a nicely machined adapter that connects the FLI CFW to the field flattener.

Here is the preliminary result with only ten 20 min light subs. The only calibration was a dark frame subtraction (i.e., no flat field correction was applied). The files were calibrated, registered, and stacked in PixInsight, then processed with a gentle pass through an Atrous Wavelet Transform (to remove some small-scale noise), then stretched with Histogram and Curves Transformations.

We were quite pleased that Alnitak was held extremely well in check (no significant halo), which suggests that the camera and 3 nm H-alpha filter did their jobs well.

We're collecting more lights and darks. I'm thinking of collecting at least thirty-six 20 min Ha subs to get more detail below the Horsehead. When the Moon is more cooperative, we'll also get RGB data, and merge it with a starless version of the H-alpha dataset.

Edited by JJK (12/13/13 12:28 AM)


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: JJK]
      #6250219 - 12/13/13 01:52 AM

I have a very similar image but with a 7nm Baader. And there's a strong halo around Alnitak.

Good to see (visually!) what all that extra cash for the Astrodon buys you...


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: orlyandico]
      #6250415 - 12/13/13 08:09 AM

So far, it seems worth the price.

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jbalsam
sage
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Reged: 07/06/12

Loc: Darnestown, MD
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: JJK]
      #6250436 - 12/13/13 08:30 AM

I have the same filters, Orlando, and I see halos around bright stars as well. Since John and I started collecting this data I've been tempted to buy at least the 3nm H-a filter from astrodon. The lack of halos is great, but what I like even more is how suppressed the background stars are. It lets the nebulosity stand out more distinctly.

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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: jbalsam]
      #6250490 - 12/13/13 09:10 AM

At $925 for the 2" 3nm... This is one that I almost certainly must pass on.

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jbalsam
sage
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Reged: 07/06/12

Loc: Darnestown, MD
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: orlyandico]
      #6250503 - 12/13/13 09:18 AM

This is when I'm glad I use 36mm filters. Still $500+ for a filter is tough to swallow. It will definitely be a "someday" purchase for me.

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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: jbalsam]
      #6250555 - 12/13/13 09:52 AM

Josh, that AT8IN you sold me dictates the 2" filters.. Since at f/3 (with reducer) the lightpath is really steep... And no, the stars still aren't round. I'm installing the Feathertouch this weekend...

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rflinn68Moderator
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: orlyandico]
      #6250606 - 12/13/13 10:16 AM

Orlando, I thought you could even use 1.25" filters with the 8300 sensors above f/5 so you might be good with a 36mm filter.

JJK, this looks great! I have been looking into the different cameras with the 8300 sensor. I had pretty much decided on the STF-8300 and going with the Astrodon 5nm filters. Maybe I should just bite the bullet and get the 3nm? I wonder how much of this (Alnitak) is the camera (FLI vs SBIG) and how much is the filter (Astrodon 3nm vs 5nm)?


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jbalsam
sage
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Reged: 07/06/12

Loc: Darnestown, MD
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: rflinn68]
      #6250728 - 12/13/13 11:19 AM

Ah... the downside of a big fast scope. I stopped trying to get round stars across the whole field with that scope after about three or four wasted nights. I attributed it to my cheaper astro-tech reducer. I've never had such headaches with a refractor

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bseltzer
Pooh-Bah


Reged: 10/28/07

Loc: East S.F.Bay, CA
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: jbalsam]
      #6250792 - 12/13/13 11:58 AM

Quote:

Ah... the downside of a big fast scope. I stopped trying to get round stars across the whole field with that scope after about three or four wasted nights. I attributed it to my cheaper astro-tech reducer. I've never had such headaches with a refractor




That's pretty much why my Newt has been relegated to visual use. Even with a Baader MPCC, I had little sea gulls in the corners with any chip larger than a KAI 2020


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: bseltzer]
      #6250903 - 12/13/13 01:12 PM

A few nights ago I discovered that Altair Astro makes a 0.6X refractor reducer.. for a hundred bucks. How good that is.. I shudder to speculate.

But Borg has a $1000 0.66X refractor reducer that would take my refractor down to f/4. Yes it's an expensive reducer but my Keller costs about that much.

Now as to why I'm still fighting this scope.. there's no way to get an f/3 focal ratio under $5000 except with this Franken-scope. The only other options are the AGO or ASA newtonians, the Officine Stellare RH200, or the Takahashi Epsilon (or the Borg 125SD with the Super Reducer, or the Tak FSQ-106 with its own reducer). All of which are too rich for my blood...


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: rflinn68]
      #6251030 - 12/13/13 02:27 PM

Quote:

Orlando, I thought you could even use 1.25" filters with the 8300 sensors above f/5 so you might be good with a 36mm filter.

JJK, this looks great! I have been looking into the different cameras with the 8300 sensor. I had pretty much decided on the STF-8300 and going with the Astrodon 5nm filters. Maybe I should just bite the bullet and get the 3nm? I wonder how much of this (Alnitak) is the camera (FLI vs SBIG) and how much is the filter (Astrodon 3nm vs 5nm)?




Than you, Orlando. It'll get better with a lot more data, and it's fun.

That's a good question. After months of thinking about which filters to get, and chatting via e-mail with others, I decided that restricting as much off-band light as possible could be important in my case. I live in a Red Zone and I want to image whenever the sky is clear, even with the Moon up.

To address an earlier point someone else raised, the 3 nm NB filters are more costly ($300 more than the 5 nm versions), but averaged over 5 years, that additional cost is in the noise.


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: orlyandico]
      #6251032 - 12/13/13 02:29 PM

Quote:

A few nights ago I discovered that Altair Astro makes a 0.6X refractor reducer.. for a hundred bucks. How good that is.. I shudder to speculate.

But Borg has a $1000 0.66X refractor reducer that would take my refractor down to f/4. Yes it's an expensive reducer but my Keller costs about that much.

Now as to why I'm still fighting this scope.. there's no way to get an f/3 focal ratio under $5000 except with this Franken-scope. The only other options are the AGO or ASA newtonians, the Officine Stellare RH200, or the Takahashi Epsilon (or the Borg 125SD with the Super Reducer, or the Tak FSQ-106 with its own reducer). All of which are too rich for my blood...




f/3 is a Brave New World in imaging. Fast, but there is a price to pay (everything has to be just right).


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: JJK]
      #6251097 - 12/13/13 03:04 PM

I'm in a white zone. With my f/6.7 refractor I need 20 minute subs with the 7nm Baader just to get anything.

F/3 is mouth-watering.. but I have to fight the non-round stars.


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CounterWeight
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Reged: 10/05/08

Loc: Palo alto, CA.
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: orlyandico]
      #6253153 - 12/14/13 06:28 PM

lots of neat information here but i wanted to start and say - 'nice work', you have a very nice image in the works there, actually to me very nice just as is too. Great halo suppression! And you have good signal everywhere - so nice work on your processing. I am curious though why you are choosing not to flat in the calibration? does that scope not vignette optically?

I used the Baader NB for about two years and 4 scopes and moving to Astrodon I do think the Astrodon a better filter - same goes for the RGBL. I'm using the 5nm and have no complaints.

On some of the other topics I always had difficulty when using various inexpensive reducers and flatteners. I take the recommended spacing as a guide and test from there. As far as I remember all were able to get a good flat field eventually (down as far as f/4.6? or so with the 8300M but it wasn't easy and I still have reservations about the bright star issue / anti reflection with all the inexpensive ones.

of all the issues that can come up, after finally getting a flat image - the terrible glare/halo issue is IMO the next worse? I'm not aware of any non destructive ways to get around it in the processing.

Goes back to that basic part of imaging of getting the best quality sub exposures to begin with and not counting on post processing to fix.

Anyway back to the start - nice work hope you have clear night to complete


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jbalsam
sage
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Reged: 07/06/12

Loc: Darnestown, MD
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: CounterWeight]
      #6256508 - 12/16/13 03:34 PM

Jim, I'll answer your question for John:

We haven't bothered flat fielding the image yet only because we haven't bothered taking flats with the new camera. The image didn't look to have noticeable/objectionable vignetting, so we didn't bother with it. We will eventually take and use flats just out of principle.

The H-a data I get with my Baader filters always shows significant and objectionable vignetting. I haven't tried using the scope that John and I used to take this image with my filters, so I don't know if the lack of obvious vignetting here is because of the filters or because of the scope.


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CounterWeight
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Reged: 10/05/08

Loc: Palo alto, CA.
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: jbalsam]
      #6257086 - 12/16/13 09:15 PM

Thanks Josh!... I have lingering questions as to in my various setups about the differences between the filters alone, though it seems to have abated in general since going to the Astrodon which is fantastic. It's an important plus, but I don't recall seeing that an advertised benefit.

You guys are off to a great start with that equipment


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Madratter
Postmaster


Reged: 01/14/13

Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: CounterWeight]
      #6257106 - 12/16/13 09:22 PM

Looks very nice.

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jbalsam
sage
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Reged: 07/06/12

Loc: Darnestown, MD
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: Madratter]
      #6257147 - 12/16/13 09:40 PM

We are planning to do a comparison that will isolate the filters as the (nearly) only source of variation. We both have KAF-8300 cameras (his FLI, my Atik). His filters are much larger than mine (I think they are the 50mm round versions, where mine are Baader's 36mm filters). We'll compare results on a single scope and see what the images look like.

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rflinn68Moderator
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: First-light test of FLI ML8300 & 3 nm Astrodon H-a new [Re: jbalsam]
      #6258525 - 12/17/13 04:49 PM

Quote:

We are planning to do a comparison that will isolate the filters as the (nearly) only source of variation. We both have KAF-8300 cameras (his FLI, my Atik). His filters are much larger than mine (I think they are the 50mm round versions, where mine are Baader's 36mm filters). We'll compare results on a single scope and see what the images look like.




I'd be very interested in seeing the results of this. Wish I could also find a 5nm vs 3nm Astrodon h-alpha comparison somewhere. I think the H-alpha will be the first filter I get after I buy my camera.


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