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.
Excellent pic Kevin, you have captured a lot of fine detail there and those defraction spikes really make the image sparkle.
Rick
Thanks Rick!
Quote:
Originally Posted by rustigsmed
nice one kevin, some good dust, how are you finding the newt?
rusty
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. 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.
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.
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
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.
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
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.
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
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!
Quote:
Originally Posted by 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.
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.
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!
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.
The tube is short, compact and not too heavy.
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. 
