Thanks Leon I tend to agree I've stacked this one excluding the 5 minute subs and used the 45 second exposures as offsets and seems to appear better in post processing. The 5 minute subs where extremely noisy as well.
Unfortunately with the Pentax you don't have the ability to control and focus via a laptop.
Trevor - hi
If your eyes aren't what they used to be, like mine, it does make focusing unnessesarily difficult. Without live view it can still be done very easily - and painlessly, with a Bahtinov mask. These are a bloke with fading visions' best friends ever. No laptop required.
Like you, I used to take a 3-second shot of a star, waited until the image appeared on my cameras LCD screen, and then judged how large the fuzzball was when zoomed in to 10x. I then took another shot after moving the focuser one way or t'other and compared the new fuzzball with the previous. I kept going until I could see a trend and then settle on a focus point where the fuzzball was the smallest. Very tedious and in this day and age of cloud. You'd most likely miss out on getting down to business for real as the clouds roll in. to ruin the night.
I now do it without any eye strain at all, and all in about a minute.
See the attached image. A Bahtinov mask creates a diffraction pattern with a cross of two static spikes - "L" left and "R" right. It then lays down a movable spike - "C" center whose lateral position is based on the quality of focus you have.
Set your approximate focus and place the mask in front of your ED80's objective. Take a 3-second exposure of a bright-ish star. If you're lucky you'll get a pattern on your zoomed LCD screen like the one in the attached photo, where the C spike is absolutely centred on the junction of the other two. If not, adjust focus a little one way or the other until you see it centred on subsequent shots. Stop when you're centred. The position is easy to see, and it's very obvious when it is not centred. Viewing a position of something like this is far more accurate than determining if a fuzzball looks tighter than it did in the last frame.
The beauty of this method is that it is super easy to see a definitive result - and you know that you have the besst possible focus you can get without spending an inordinate amount of time doing it.
Omaroo, thanks for that when I've taken shots for focussing I try what you described firstly although I've never been able to get a perfectly round fuzzy circle although close and I get tiny little lumps at 0,90,180, etc is this usual through the 80ED.
Also I've made up one of these masks but even with it have'nt had a great success but I need to percervier.
Also I've made up one of these masks but even with it have'nt had a great success but I need to percervier.
No worries Trevor.
What you really must do is find a BRIGHT star (but not a bright planet such as Venus) like Canopus or Achenar with the 80mm aperture of your scope. This is an absolute must on scopes with small apertures - and my FS-102 is no exception either. Take a good 3-second shot and make sure you zoom in to it on your LCD. At 10x or so (presuming the Pentax lets you zoom) you'll easily see the spikes.
Gee Trevor, I dont want to be discouraging, but this second attempt looks worse than the 1st one, you seem to have a bunch of problems there. Check Leinads M42, he has similar gear, whats up?. The noise is overwhelming.
Gee Trevor, I dont want to be discouraging, but this second attempt looks worse than the 1st one, you seem to have a bunch of problems there. Check Leinads M42, he has similar gear, whats up?. The noise is overwhelming.
Exactly my point could someone take a series 2 minute darks with their Canon at ISO800 and post it so I can compare to mine.
I might need to drop the ISO back to 400, the noise from the Pentax seems high refer to images below both a 2 minute exposures at ISO800 taken on th 5/12 of M45 1 hr apart
Attached are two images of a star I focused on last night the second at 100%
hows my focus ???
Hey Trev, is that in-camera sharpening that's occuring?
I notice that dark border line when I sharpen too much, or levels arent right.
It's unfortunate that the camera isnt supported for Imaging Software. I use Nebulosity 2 at the moment with the 350D, and I can Fine Focus and Frame and Focus, which are quick and easy, powerful tools via laptop. Judging by eye I tried to do before; and checking via LCD screen for best focus on the camera is tricky.
I admire your persaverance with limited options; I'd have easily lost my patience.
Quote:
Originally Posted by TrevorW
Exactly my point could someone take a series 2 minute darks with their Canon at ISO800 and post it so I can compare to mine.
I might need to drop the ISO back to 400, the noise from the Pentax seems high refer to images below both a 2 minute exposures at ISO800 taken on th 5/12 of M45 1 hr apart
Cheers
I dont have any Darks at 2min,ISO800, but here's 1 Dark at 5mins ISO400 I took from the other night.
Does your camera have built-in CWB, or the ability to add/edit CWB? Just wondering.
I guess the best advice would be from someone with the same camera? Hope any of this may help..
Thanks Leinard in does have in camera sharpness should I drop this back to the negative in and set WB for daylight also I believe with the Canon they use a CMOS chip which is quieter than a CCD and your dark is dark, mine are noisy
