help: too many stars!

[rockyraccoon]

Hello good people of SL, I am a newcomer to the world of astronomy and astrophotography.

I am a total novice but I think I got acceptable (to my standards at least... ) results with large bright objects such as M42, IC434, M45. (I'm using hyperlinks to minimize downloading time for folks with slow connections).

However I'm struggling with the processing of images that present too many stars, which make it hard to emphasize the nebulosity without making the stars bloat or saturate the field.

For example: NGC2244, IC1805, IC405, IC410.

In all cases I'm stacking 30-40 30s subs in MaximDL, and then applying level and curves in PS.

My tool of the trade is an unguided 8" Edge HD OTA, Alt-Az mount, with an ATIK 314L+ (color) attached via an Hyperstar 3.

I would be happy to share the raw (stacked) fits files.

Critique and advice much appreciated! Thanks.

[jgs001]

I'm not an expert, but this toolset might help...

Tony Kuyper Photography?Using Luminosity Masks?Introduction

The technique creates selections for you based on the brightness of the contents of the image.

[ollypenrice]

You could try Noel's Actions for Photoshop, now under the Prodigital brand. There's a 'Make Stars Smaller' action.

It's odd but you are not getting much star colour. I don't know why.

The first thing to be sure of is focus. This will have a monumental effect on final star size and is always going to be a devil to get right with a system as fast as the Hyperstar, especially since the moving mirror focus system is a very blunt instrument. Do you have an upgraed electronic focuser? This would a first step, I think. And how are you focusing? Presumably you can't use a Bahtinov with the Hyperstar so are you using FWHM? If so, spend a very long time on it. Ten minutes or so.

I'd use longish focusing subs to average out the seeing, something like four seconds.

Olly

[rockyraccoon]

Thank you Olly, you raise some good points. Indeed, I would like to exclude acquisition issues before starting to mess about with post processing filters.

I don't know why I don't have much star color either: I have to say that when I look at the subs being acquired, the colors seem to be there.

Regarding Hyperstar and focusing issues:

- I have no issues using a bahtinov mask, since the dew shield protrudes a good few inches past the camera.

last night I have double checked that what seems to be best focus via bahtinov mask actually correlates to smallest FWHM value and it does (as you would expect).

I never thought about using subs as long as 4s for focusing, although your reasoning makes a lot of sense (avg out the seeing). I guess I will try again with dimmer stars.

- I don't have an electric (or feedback controlled) focuser, but I do have a feathertouch micro focuser that seems to work very well

- My OTA (it's an edgeHD) has locking screws (I'm not sure that this what they are called) for the primary mirror, so the mirror doesn't really move when slewing.

Thanks again for the feedback! Much appreciated...

You could try Noel's Actions for Photoshop, now under the Prodigital brand. There's a 'Make Stars Smaller' action.

It's odd but you are not getting much star colour. I don't know why.

The first thing to be sure of is focus. This will have a monumental effect on final star size and is always going to be a devil to get right with a system as fast as the Hyperstar, especially since the moving mirror focus system is a very blunt instrument. Do you have an upgraed electronic focuser? This would a first step, I think. And how are you focusing? Presumably you can't use a Bahtinov with the Hyperstar so are you using FWHM? If so, spend a very long time on it. Ten minutes or so.

I'd use longish focusing subs to average out the seeing, something like four seconds.

Olly

[ollypenrice]

Well tonight I've just seen a Hyperstar in action for the first time and you are right about the mask on the dewsheild. Hadn't thought of that. Doh!

The owner is using the free Bahtinov Grabber for foucus. Seems good, though I think that you'd get very close by eye. I must say that my initial doubts about the system are disappearing fast as I see a nice crisp focus being acheived.

Best of luck,

Olly