IC348 hybrid image.

[ollypenrice]

Inspired by Fegato's excellent recent image of this target, I went back to two sets of data I have on it and combined them. The first was refractor-CCD-HaLRGB captured with Gnomus and Mrs Gnomus some time ago, the second a recent CMOS-OSC-RASA 8 set with Paul Kummer. Having StarXterminator was a huge bonus when stretching the faint dust.

Olly

[gorann]

Brilliant Olly with soft and yet sharp dust. (For perfection you may want to crop the artifact along the left edge).

Göran

[Fegato]

Really nice Olly - more than matched my dust, and the Ha gives it a nice pop! 

Robin

[ollypenrice]

2 minutes ago, Fegato said:

Really nice Olly - more than matched my dust, and the Ha gives it a nice pop! 

Robin

In intensity but not in delicacy, I think.

Olly

[Rodd]

Do you use a RASA. Any thoughts?

[Knight of Clear Skies]

In infra-red, we can see IC348 is part of an enormous complex:

http://viewer.legacysurvey.org/?ra=54.8166&dec=32.0311&layer=unwise-neo6&zoom=9

I think the visible part is at upper-left.

[ollypenrice]

7 hours ago, Rodd said:

Do you use a RASA. Any thoughts?

I do. It's brilliantly good in most respects but not perfect. It's very fiddly to set up with good collimation and no tilt. Stellar images are not always top class but, using star removal and replacement, this matters much less than it used to. We've also discovered some broad arc-shaped artifacts in some captures. They can be cosmetically repaired but the origin is as yet unknown. Would I swap it for anything else of comparable focal length? No, I'll work round the issues because the speed is phenomenal.    It's a different world.

Olly

Edit: I'd add that it may not be for pixel peepers. It's a broad brush instrument which, above all, goes deep and is magnificent wherever there is dust.

Edited November 28, 2022 by ollypenrice
Clarification

[Fegato]

5 minutes ago, ollypenrice said:

I do. It's brilliantly good in most respects but not perfect. It's very fiddly to set up with good collimation and no tilt. Stellar images are not always top class but, using star removal and replacement, this matters much less than it used to. We've also discovered some broad arc-shaped artifacts in some captures. They can be cosmetically repaired but the origin is as yet unknown. Would I swap it for anything else of comparable focal length? No, I'll work round the issues because the speed is phenomenal.    It's a different world.

Olly

re: the arc shaped artifacts - are they like the "rainbow" ones in this thread?

https://www.cloudynights.com/topic/804923-rasa-11-problems-with-reflectionsrainbows-caused-by-bright-stars/

There's a problem with reflections from the lens group when using a wider image train than that provided by Celestron (e.g. Baader UFC, full Octopi interface), and I suffered from this with many images - every bright star close outside the frame (and sometimes inside) caused it. Various tests narrowed it down to the RASA lens group itself, not the attachments.  I have a small circular piece of flocking blocking the very outside of the lens group glass (as seen in the thread), and this has completely stopped any artifacts.

I keep meaning to send a dossier to Celestron for their info, but haven't got round to it, although whether they'd do anything about it I don't know.

[Rodd]

1 hour ago, ollypenrice said:

I do. It's brilliantly good in most respects but not perfect. It's very fiddly to set up with good collimation and no tilt. Stellar images are not always top class but, using star removal and replacement, this matters much less than it used to. We've also discovered some broad arc-shaped artifacts in some captures. They can be cosmetically repaired but the origin is as yet unknown. Would I swap it for anything else of comparable focal length? No, I'll work round the issues because the speed is phenomenal.    It's a different world.

Olly

Edit: I'd add that it may not be for pixel peepers. It's a broad brush instrument which, above all, goes deep and is magnificent wherever there is dust.

How about in poor skies?  For me, even 30 sec lum with fsq at f3 is to much except on rare occasions due to LP. And 4-5 hours of 30 sec subs starts to get old very fast, especially when even that is not nearly enough.  I was told by tak that epsilon’s are not recommended for skies with LP. What about the RASA?

[ollypenrice]

1 hour ago, Fegato said:

re: the arc shaped artifacts - are they like the "rainbow" ones in this thread?

https://www.cloudynights.com/topic/804923-rasa-11-problems-with-reflectionsrainbows-caused-by-bright-stars/

There's a problem with reflections from the lens group when using a wider image train than that provided by Celestron (e.g. Baader UFC, full Octopi interface), and I suffered from this with many images - every bright star close outside the frame (and sometimes inside) caused it. Various tests narrowed it down to the RASA lens group itself, not the attachments.  I have a small circular piece of flocking blocking the very outside of the lens group glass (as seen in the thread), and this has completely stopped any artifacts.

I keep meaning to send a dossier to Celestron for their info, but haven't got round to it, although whether they'd do anything about it I don't know.

Robin, we greatly appreciate your providing this link and information.  Many thanks. I would say that these probably are, indeed, our arcs, more or less. Ours are not rainbow-coloured but show up very strongly in the blue channel. It's perfectly normal for blue to be the most affected. In the past I've used a simple compass-cutter to cut circles out of the thin plastic top of a margarine tub.

One snippet I can contribute to the discussion is that the 'instant test' for seeing if the arcs are there is the Equalize feature, under Image-Adjustments in Photoshop. It makes them screamingly obvious. It's also a good way to check mosaic joints.

Olly

[ollypenrice]

36 minutes ago, Rodd said:

How about in poor skies?  For me, even 30 sec lum with fsq at f3 is to much except on rare occasions due to LP. And 4-5 hours of 30 sec subs starts to get old very fast, especially when even that is not nearly enough.  I was told by tak that epsilon’s are not recommended for skies with LP. What about the RASA?

I don't know, Rodd, but I'll ask a friend who does to comment on that.

Olly

[Fegato]

13 minutes ago, ollypenrice said:

Robin, we greatly appreciate your providing this link and information.  Many thanks. I would say that these probably are, indeed, our arcs, more or less. Ours are not rainbow-coloured but show up very strongly in the blue channel. It's perfectly normal for blue to be the most affected. In the past I've used a simple compass-cutter to cut circles out of the thin plastic top of a margarine tub.

One snippet I can contribute to the discussion is that the 'instant test' for seeing if the arcs are there is the Equalize feature, under Image-Adjustments in Photoshop. It makes them screamingly obvious. It's also a good way to check mosaic joints.

Olly

No problem Olly - I should give credit to Daniel Gallo who created that thread who came up with the solution. It doesn't seem ideal to be blocking some of the light path out of the lens group, but it does the job, and I can't say I've noticed any degrading of images. With mine, I took the glass out of the Celestron screw in clear filter (which I wasn't using), and used that to hold it in place and stop it moving around.

Thanks for the photoshop hint. 

 

 

 

 

[Fegato]

52 minutes ago, Rodd said:

How about in poor skies?  For me, even 30 sec lum with fsq at f3 is to much except on rare occasions due to LP. And 4-5 hours of 30 sec subs starts to get old very fast, especially when even that is not nearly enough.  I was told by tak that epsilon’s are not recommended for skies with LP. What about the RASA?

I suspect it might be a bit frustrating - the RASA will obviously gather the LP very quickly!  I max out at 30s for broadband subs in Bortle 3, so it will be much shorter in severe LP. You could end up with a hell of a lot of subs! And the real subtle dusty stuff that the RASA excels at probably won't appear anyway.

And with narrowband, you're limited to dual narrowband filters that are designed for fast systems - e.g. IDAS NBZ, which I use.  The NBZ is 10nm bandpass for Ha and OIII. I would guess the best bet for severe LP is to go very narrow, and that really means going mono. This would be a pain with a RASA, as you can't use a filter wheel as it blocks too much of the light path, so you'd have to manually change with a filter draw.

[AMcD]

17 minutes ago, Fegato said:

This would be a pain with a RASA, as you can't use a filter wheel as it blocks too much of the light path

I have often wondered whether they could design what might be called a 'filter cube' for the RASAs, at least for narrowband.  This would be a cube with openings for the light path at the front and back and enclosing a cylinder mounted across and rotating within the light path. The three narrowband filters would be mounted on the circumference of the cylinder with a hole opposite.  As the cylinder rotated, the filter and its corresponding hole would enter the light path.  The profile of such a gizmo would certainly be smaller than the filter wheel.  Just musing over my lunch...

[Rodd]

1 hour ago, Fegato said:

so you'd have to manually change with a filter draw.

This by itself would not be an issue as I change filters only after long periods.  But the other issues give me pause for sure

[Fegato]

2 hours ago, AMcD said:

I have often wondered whether they could design what might be called a 'filter cube' for the RASAs, at least for narrowband.  This would be a cube with openings for the light path at the front and back and enclosing a cylinder mounted across and rotating within the light path. The three narrowband filters would be mounted on the circumference of the cylinder with a hole opposite.  As the cylinder rotated, the filter and its corresponding hole would enter the light path.  The profile of such a gizmo would certainly be smaller than the filter wheel.  Just musing over my lunch...

Sounds like it should be feasible doesn't it - a sort of circulating triangular thing inside the tube?  Only problem would be the very limited back focus distance. So might be out of the question with RASA 8 I think, but you might be able to squeeze one in on a RASA 11, although with minimum 2" filters needed, it would be tight (I've got just about exactly 2" of filter draw and extenders on mine) -  you might need to allow it to circulate into the space at the front near the lens group (but with the filter at the back as near to the camera as possible to reduce vignetting). 

[mftoet]

5 hours ago, ollypenrice said:

I don't know, Rodd, but I'll ask a friend who does to comment on that.

Olly

Having owned an Epsilon-180ED (f/2.8) for about 10 years now and living in an agglomeration of large cities (SQM 18.5, Bortle 8/9) Olly asked me to chime in. By the way, excellent image, Olly!

In my garden roll-off roof shed, I only use the Epsilon with Baader ‘Highspeed’ narrowband filters. The light pollution here is too severe for not using narrowband filters. I’ve owned an IDAS P2 light pollution filter in the past, but that resulted in rainbow circles/gradients that could not be dealt with using gradient removal software. Maybe those gradients were caused by a band shift issue. However, considering light pollution, my situation is probably out of the ordinary for typical city skies. I live in an area with a lot of agriculture for growing flowers and vegetables by using assimilation lights. People who don’t live here and visit the area for the first time have often mistaken the bright light domes above the greenhouses for a big fire in a city ahead.

I don’t longer bother pursuing broadband deep sky photography from where I live. There isn’t much to enjoy, seeing just a hand full of stars. I sometimes compare broadband deep sky photography (or visual deep sky astronomy) from my home town with trying to coral dive in a mud puddle…

[ollypenrice]

33 minutes ago, mftoet said:

Having owned an Epsilon-180ED (f/2.8) for about 10 years now and living in an agglomeration of large cities (SQM 18.5, Bortle 8/9) Olly asked me to chime in. By the way, excellent image, Olly!

In my garden roll-off roof shed, I only use the Epsilon with Baader ‘Highspeed’ narrowband filters. The light pollution here is too severe for not using narrowband filters. I’ve owned an IDAS P2 light pollution filter in the past, but that resulted in rainbow circles/gradients that could not be dealt with using gradient removal software. Maybe those gradients were caused by a band shift issue. However, considering light pollution, my situation is probably out of the ordinary for typical city skies. I live in an area with a lot of agriculture for growing flowers and vegetables by using assimilation lights. People who don’t live here and visit the area for the first time have often mistaken the bright light domes above the greenhouses for a big fire in a city ahead.

I don’t longer bother pursuing broadband deep sky photography from where I live. There isn’t much to enjoy, seeing just a hand full of stars. I sometimes compare broadband deep sky photography (or visual deep sky astronomy) from my home town with trying to coral dive in a mud puddle…

Thanks Maurice, I'm sure this will help Rodd.

Olly