Oh no not another Eta Carina ;-)

[cometcatcher (Kevin)]

A rare thing happened on February 11, it fined up for a few hours at night. Must have been for my birthday. But what to do with a 3/4 moon in the sky. Shoot the moon? Nah. Let's experiment with deep sky.

Over in the big boy's toys forum section there's some really lovely Bi-Colour shots so thought I'd have a crack at that using an achro refractor, some string, garbage bag, glue and duct tape. I have a Ha filter but not an OIII. To simulate an OIII filter I used a 48mm Hoya X1 green filter stacked onto a Baader Semi-Apo filter. This should allow through a fair bit of OIII, I thunk.

So here's the mess, um... pics that resulted. From last to first, the B+W image is 10x3 minutes of Ha. The yellow mess is 10x3 minutes of Ha mapped to the red channel, 10x3 minutes of psuedo OIII mapped to the blue channel and a combo of Ha and psuedo OIII mapped to the green channel. I think I got that right. The red pic is Ha to red, OIII to green and blue channels. Taken through a SW120 F5 achro refractor and Full Spectrum Nikon D70s. The experiment didn't really work out as I intended. Maybe due to not using a real OIII filter. Oh well better luck next time.

Which one do you like best?

[Amaranthus (Barry)]

Fine work and nice FOV. Out of curiosity, what process did you use to stack the 3 images (I've been playing around with a few different methods)?

[cometcatcher (Kevin)]

Just in Photoshop Barry. I make a new image and copy the Ha and OIII into the respective channels using the Layers / Channels / Paths window. By selecting an individual channel it's also possible to align and rotate each channel to match the position of the other channels.

[rcheshire (Rowland)]

Great work Kevin. Very nice indeed.

[cometcatcher (Kevin)]

Thanks Rowland.

[Kugelblitz (Marcus)]

Originally Posted by cometcatcher

using an achro refractor, some string, garbage bag, glue and duct tape.

Channeling your inner MacGyver there eh?

Nice images you got out of it, I especially like the first (red) one.

[cometcatcher (Kevin)]

Originally Posted by Kugelblitz

Channeling your inner MacGyver there eh?

Hehheh, yeah that's me. Although I'm yet to figure out how to make a 10:1 reduction focuser out of wood.

[Amaranthus (Barry)]

How do you find the SW120 f5 as an overall performer, Kevin? I'm thinking of getting one for some rich-field visual work, and maybe mounting it properly for some astrophotography...

[cometcatcher (Kevin)]

Originally Posted by Amaranthus

How do you find the SW120 f5 as an overall performer, Kevin? I'm thinking of getting one for some rich-field visual work, and maybe mounting it properly for some astrophotography...

Barry, for visual it's absolutely brilliant. There's CA on bright objects but for DSO's it's great. Stars are pin point. Not sure how it is on planets as I haven't tried. I would suspect not so good.

For photography... well it's hard to tame. The CA is bad. For dim star fields and nebula you can get away with it. But in a bright star field like M42 and one shot colour, it's pretty horrid. See attachment with no processing. With a nebula filter and post processing it cleans up a lot, but not completely.

It's awesome for comets, which I like to use it for both visual and photographic. I think I get away with it for comets because they are almost always faint and the star fields get blurred out by trailing as I track on the comet so the CA doesn't get a chance to "build".

Narrow band filter imaging should be okay also, but there is a focus shift between filters. I find the focuser okay for visual but a pain for photo work. When I get some $ to spare I want to upgrade it.

Here it is with a Mizar 68mm f8.8 guidescope on an HEQ5 pro. They are both 600mm focal length. The SW120 is also shooting through an Orion field flattener.

I'm after the F8.3 version of this scope if I can get one for a good price second hand. New they cost nearly as much as an ED scope. CA is always better at higher F ratios.

[Amaranthus (Barry)]

Thanks Kevin, that's very helpful. For a while at least, I'd be concentrating on visual with it, sitting nice in TFOV terms between my C8 SCT (which I use as a work horse for planetary and smaller DSO) and my 15 x 70 binocs. I'm really after an 'in betweener' that allows me to visualize the larger DSO, and for general rich-field sky scanning (and is also portable). I've got some nice eyepieces to put on in (!) so it sounds like it would do the job I'm after really nicely...

I can see the challenge in using it for astrophotography - I guess I can just tinker away and see what I come up with over time. Do you know if it's possible to get a dovetail bracket for it? (I was thinking of sometimes putting it on my 8SE GOTO mount)

[cometcatcher (Kevin)]

Originally Posted by Amaranthus

Do you know if it's possible to get a dovetail bracket for it?

Not quite sure what you mean but the brackets that come with it just screw into the holes in the mounting plate that came with my HEQ5 pro goto. I just made the wooden plate to accommodate the guidscope along side.

[Amaranthus (Barry)]

My GOTO mount uses a Vixen-style bar (1.75” wide). Should be no issue I think - I can probably make one out of wood that fits.

[cometcatcher (Kevin)]

The bar on the HEQ5 pro is about 1.75". Might be the same thing?

[nebulosity. (Jo)]

Nice one Kevin

Cheers
Jo

[Amaranthus (Barry)]

The bar on the HEQ5 pro is about 1.75". Might be the same thing?

It may well fit directly then! The SE mount has a squeeze clamp mechanism to attach the OTA, rather than screws/bolts.

[cometcatcher (Kevin)]

Originally Posted by nebulosity.

Nice one Kevin

Cheers
Jo

Thanks Jo. It was just an experiment really to see what would happen if...

Originally Posted by Amaranthus

It may well fit directly then! The SE mount has a squeeze clamp mechanism to attach the OTA, rather than screws/bolts.

Yeah that sounds like the bar that goes on to the HEQ5, but the SW120 didn't come with that so you may need another dovetail bar. I think they are fairly cheap.