M42 in 12 minutes with the 8" F4

[cometcatcher]

Just a 12 minute quickie before the Moon rose with the new toy. Makes me wonder what a few hours would do.

24 x 30 seconds for the main and a couple of shorter subs for the core through the 8" F4 unguided at ISO1600, Baader MPCC MKIII, Pentax K-5.

[ZeroID]

And the imaging speed race has just started .. looks pretty dang good to me. Best Running Man I've seen in a while. M42 is still not high enough for me while I'm awake. I'll get to it later in the year.

[cometcatcher]

I think Rick won that race in 15 seconds lol.

[rustigsmed]

nice one kevin, some good dust, how are you finding the newt?

rusty

[multiweb]

Nice one Kevin. Really cool colors. :thumbsup:

[doppler]

Excellent pic Kevin, you have captured a lot of fine detail there and those defraction spikes really make the image sparkle.
Rick

[cometcatcher]

Thanks Marc!



Thanks Rick!



Well.... it's taking a bit of getting used to. There's the good and the bad.

For the good, as you can see it does seem to be fast compared to my ED100 refractor. This pic at astrobin needed 4 hours in cool weather. http://astrob.in/118167/0/ though it is deeper. It's possible to go fairly deep with short subs therefore doesn't really need guiding for a quick flirt. ;) The tube is short, compact and not too heavy.

The bad. Collimating it at F4 is tricky. Very tricky. I was mucking about with it for 2 hours last night and I don't think I'll ever get it perfect. The main mirror cell design is screwy. :screwy: I would do it differently if I was building one. The springs are too light duty and the tightening bolts move the mirror cell. With my homebuilds I simply use 3 very heavy duty bolts and springs which work better than this.

The central obstruction is large and loses light. The F ratio might be 4 but the T stop is more like around 4.8. It's probably equal to a good 5 or 6 inch refractor.

Tube currents are worse than refractors.

But it's a lot cheaper than an equivalent refractor and that's why I got it.

[LightningNZ]

Pathetic collimation springs seem to be the single most complained about feature of these mass-produced Newts.

[rustigsmed]

replacement springs are pretty much mandatory on a GSO unfortunately...

my 12" GSO was literally useless without replacement springs, whereas my Skywatcher 12" is still running fine on its original springs. I also think the gso spider vane is more flimsy.

[cometcatcher]

Yeah I think the Skywatcher CF models are better suited to imaging. But more expensive.

Maybe I should build an 8" F5 one day and make a decent job of it. Keep the focuser profile low, the flat smaller and make a decent mirror cell.

Just need one of those "roindtooits" that I am in short supply of lately. :P

[rustigsmed]

atleast springs are cheap to replace (and easy to do), which begs the question why don't they just put better ones in to begin with :shrug:

[doppler]

I know what you mean, I have a lot on back order and the list just keeps getting bigger. :lol:

[SimmoW]

Nice one! Good n quick, yes the speed contest has begun!

[5ash]

Nice picture Kevin , like you I have been drawn to the dark side and purchased a SW CF 8" F4 newt several months ago.. However with my setup I've had to shorten the springs( replaced them with disc springs) and am replacing the twin screwed eyepiece holder with a more secure Telescope express self centering one ( waiting for delivery)and have yet to check the focusers collimation.
Regards philip

[cometcatcher]

Disc springs, I never thought of those. The ones that are on it at the moment are very short. Compressed less than a cm.

From memory you have a SW120mm ED refractor also? Will be interesting to compare the newt to it. I don't think you will see much difference.

I've been spoiled rotten since I've been using my refractors. Wonderful scopes for lazy people like me. Going back to newts is painful. The longer F ratio ones for visual were fine, but as we know these fast newts for photo use require precise adjustment.

[5ash]

Hi Kevin,
I did a few estimates before I bought it and came to the conclusion it would be at least 2x as fast as the 120ed, however no plug and play as with a refractor! May be worth the effort , will have to see .
Regards philip

[kosh]

Very nice for a quickie Kevin. I'm struggling with the collimating too. Spent a while thinking all was good using a laser collimator then realised the secondary is out :(
Keep up the good work.

Goran.

[cometcatcher]

Refractors have few losses compared to reflectors so it will be very interesting to see the comparison. Comparing to my ED100, it looks to me to be twice as fast, where if no losses were involved it should be 4x. I guess I'll just have to sell the house, buy an APO 8" refractor and live in a tent!



Thanks Goran. I collimate by eye, by star test and by taking a short image with the camera and looking at the star shapes in different parts of the frame. Even then I find it tricky.

[NeilW]

Hi Kevin,

As a fellow K-5 owner I'm interested to know how you timed the subs. Did you use an intervalvolmeter, manual remote and a timer, or PK Tether? Oh for a Pentax version of Backyard EOS! :(

Cheers,

[cometcatcher]

Hi Neil, I use an IR remote and press the button every time for the next sub. Intervalometers are cheap and many use those. I like being at the scope during capture anyway to dodge clouds etc so it's not a problem for me. I can't remember if the inbuilt intervalometer works in manual mode or not. It may do, will have to check.

[NeilW]

I bought a fairly inexpensive intervalvometer from eBay and it works pretty well. Similarly, I've never tried the camera's internal multiple exposure capability. Excellent shot by the way. I have a SW BD 180mm F5 newt tucked away in a corner, and I've never used it for AP, preferring the ED80, but now you've encouraged me to give it a try...:thumbsup:

[cometcatcher]

Hang on, I have tried it on manual and it does work. My memory is a bit screwy sometimes. I guess I still prefer the remote though.

[Rex]

Kevin that's an awesome shot mate. I see your getting your new toy in order. Collimation can be tricky with the F4's as you said. It took me a while to get mine like it is, and I'm still not sure it is exact. The most important thing I found with the f4 as apposed to my f5 that I have, was the placement of the secondary mirror. Took me ages to get the secondary in just the right spot so that the primary is not truncated after making the collimation adjustments. I also had some focuser tilt that a while to sort out. Your doing really well to get such detail with just 12 minutes mate, so your's can't be too far out. Great job.

[cometcatcher]

Thanks Rex. There's still some slight flare at the bottom of stars. It's good enough for comets but for objects like star clusters where needle point shapes are required, my collimation falls a bit short. What's really annoying is I get it nearly there, do an adjustment and I can't get it back to where it was before I messed with it lol.

Last night's comet PanSTARRS. Does a pretty good job of comets and that's what I got it for.

[andyc]

Short subs are in fashion! Very nice Orion neb Kevin, and a great result from 12 minutes image time. I hope you can resolve your collimation issues, looking forward to more great comet (and other) images from your new toy :thumbsup:

[cometcatcher]

Thanks Andy. Short subs are also good for summer with an uncooled DSLR. Helps keep the noise down.

[NQAstro]

Very nice Kevin, now I'm getting excited i still need to get decent guiding on my HEQ5. On a side note how did u decrease the brightness of the trapezium? with my G3 CCD it completely washes out halve of the nebular. I do have an old Sony A100 but i can only use it with 100-80 ISO I might give it ago tonight and see the differences with brightness of the trapezium, Or can this be done in photoshop. I know that if I take RAW files with the DSLR I can adjust a lot of the settings. Cheers Chris

[cometcatcher]

Hi Chris, I take shorter subs for the trap and core and combine them in Photoshop using layers.

This is one way to do it. http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM