1st attempt with dslr

[ardbeg74]

Hi Guys,

Finally a bit of semi clear sky last night before the inevitable roll in of the clouds. Got out, got aligned and gave the dslr a try.

Took the below prime focus on the pl, a rather haphazard selection of 13 lights, 11 darks and 10 bias, 10sec @ 400 iso. Stacked with DSS and Levels in PS.

The orange star is, i believe, Sigma Persei. I wasnt so much going for a particular target, first time and all that, just wanted to see what would happen.

One thing i noticed after stacking is a large circular area in the center of the pic, Ive reduced this somewhat with PS but curious about what it is. Im assuming that its vignetting as its perfectly centered and circular... However the vignetting im used to with a-focal is hard with nothing visible outside the circle. However this is more a brightening of the area under the circle ( or a reduction of light outside the circle if you like). Boosting saturation shows it as red noise.

Does that sound like vignetting?

Unfortunately i didnt get to try out longer exposures or other iso settings, or other targets for that matter, but happy that i got something to play with. Surprised how many stars appeared. Due to the sky conditions, these wernt visible with an ep so i got to see something i wouldnt have otherwise.

My stars seem reasonably round i think so i now know i can get 10 sec , i believe there may be a bit of camera shake though, the long tube pl on the eq3-2 would make a pretty good seismometer. Even with the 10sec camera delay it was very much a case of "light the blue touch paper and stand well back".

So the remote trigger is on my list. Next time i'll push the exposure time and see how long i can get without trailing

Any comments, tips, things to try would be most welcome!

All the best,

Mark

[Alien 13]

Hi the lighter circle you mention is vignetting that can be improved by taking flat frames another useful tip it to use the multi shot feature it does a 10 second countdown then takes up to 10 shots at the set exposure.

The image is not bad and im sure you can push the EQ3-2 a bit more with good PA i can get up to 2mins at 400mm FL but find 30-45 seconds captures a fair amount of detail you might also want to try shooting at 800-1600 iso the camera should be ok at these settings.

The main thing is to keep at it the images nearly allways get better.

Alan

[ardbeg74]

Hi Alan,

Thanks for the tips mate, will create some flats and give that a go. Thats great about the multi shot!!! that will really save a lot of time and let me get more subs.

Next clear night i'll start at 30sec iso 800 and 1600 and see how it goes. When i get the remote i'll be able to use bulb mode and get longer... if my PA is good enough that is:)

Ive really been working on my PA though, most of last night was all PA practice, still undecided as to getting a polar scope.. been using the manual "rotate around the ncp" method and with the 40mm ep i can actually see where it should be. Not the most accurate method granted... but might give the ccd align method a go if i get cloud free long enough to set up the laptop  Dont really want the faff with setting up a polarscope if i can avoid it, would rather spend the money on an autofocuser...

Just need clear skies again!!!

Cheers

Mark

[Russe]

Nice and good first effort! +1 on the vignetting. Do FLATS to try and get rid of that, otherwise you might consider gradientexterminator for photoshop.

Leave the ISO at 400. No point in going any higher:

http://www.blackwaterskies.co.uk/2014/01/do-high-isos-make-dslrs-more-sensitive.html?m=1

[Russe]

As well - u can build up a darks library in your freezer for different temperatures at your preferred exposure lengths. No need to do them at nights...

[Russe]

And, same goes for bias frames: 50-100, temp doesn't matter:

http://www.blackwaterskies.co.uk/2013/09/pixinsight-dslr-workflow-part-1-bias.html?m=1

[Alien 13]

Hi Mark

The polarscope would make a big difference it is an effort getting the initial alignment done and getting your head around using the hour angle from stellarium but with practice you can be set up and ready to go in minuites.

Alan

[ardbeg74]

Thanks Russe!!! Awesome article on ISO. This makes perfect sense to me, dont have an ISO setting on the ASI, its gain. Photographers have always used iso/asa so makes sense for the industry to add an ISO setting to dslr's rather than a gain knob like a marshall amp

This is great to know and as i enabled the 'H' setting for iso...  i guess that means my camera goes up to 11

I actually used the H setting while getting in focus, positioning the shot and although its really noisy it helps tons but i was right to back it off to 400. Will try 200 as well and obviously get those flats and bias made up. Having them ready baked is going to leave more time for subs and darks!!!

I'll read up on the bias shots tonight.

Cheers

Mark

[ardbeg74]

Hi Mark

The polarscope would make a big difference it is an effort getting the initial alignment done and getting your head around using the hour angle from stellarium but with practice you can be set up and ready to go in minuites.

Alan

Hi Alan,

I guess the bit I'm worried about is the initial alignment when fitting the finder, seems like i need a target in the distance but alas, from my back garden there is nothing terrestrial far enough away.

I'd have to use a tree branch which might be something like 25m distant?? Thats going to create a large error in alignment isnt it? So that means im going to have to do it in the dark trying not to fall over, drop screws on wet grass etc

The other thing that worries me is actually being able to see anything. Just looking through the mount without a polar scope i really struggled to get polaris in there And with my sky glow its not always obvious that its in there when looking through such a small aperture.

But maybe its just practice and perseverance i need

Cheers

Mark

I guess

[Alien 13]

Hi Alan,

I guess the bit I'm worried about is the initial alignment when fitting the finder, seems like i need a target in the distance but alas, from my back garden there is nothing terrestrial far enough away.

I'd have to use a tree branch which might be something like 25m distant?? Thats going to create a large error in alignment isnt it? So that means im going to have to do it in the dark trying not to fall over, drop screws on wet grass etc

The other thing that worries me is actually being able to see anything. Just looking through the mount without a polar scope i really struggled to get polaris in there And with my sky glow its not always obvious that its in there when looking through such a small aperture.

But maybe its just practice and perseverance i need

Cheers

Mark

I guess

Trying to do the initial setup in the dark would be a nightmare, the setup requires putting the RA axis almost horizontal but it could be done through a bedroom window facing the front of the house i find TV arials the best target .

Alan

[Russe]

Hi Alan,

I guess the bit I'm worried about is the initial alignment when fitting the finder, seems like i need a target in the distance but alas, from my back garden there is nothing terrestrial far enough away.

I'd have to use a tree branch which might be something like 25m distant?? Thats going to create a large error in alignment isnt it? So that means im going to have to do it in the dark trying not to fall over, drop screws on wet grass etc

The other thing that worries me is actually being able to see anything. Just looking through the mount without a polar scope i really struggled to get polaris in there And with my sky glow its not always obvious that its in there when looking through such a small aperture.

But maybe its just practice and perseverance i need

Cheers

Mark

I guess

Put your scope in the back of your car and take it to a park on a nice weekend! Don't try to align at nights!!

[ardbeg74]

Hehe yea I'd do that if I had one Can hire one though so I might just bite the bullet and buy a polar scope.  Eyeballing the NCP is fine for planetary but its never going to cut it for long exposures. Even though i think ccd drift aligning is cool ( tried it with my asi but naturally the program didnt detect the camera  ) it means lugging the laptop, extension cable etc out every time... and there are times like tonight where i just want get out without all the baggage

Speaking of which, got 2 hours out tonight before the clouds got too much. Tried a lot of different iso's and exposures. Orion was visible too, thats getting hard for me now as its setting behind my house earlier and earlier. So DSS is stacking that at the moment No flats though, need to read up a bit on that. But i guess if i can duplicate the camera orientation again i could make some for last night and tonights data?

The links and other articles on that blog site are great btw. Enjoyed reading them on the way home. So thanks for that!!!

clear skies mate

cheers

Mark

[Russe]

To recreate FLATS is not really gonna work. But why don't you try - it's all a learning experience...

The only callibration frames you'd have to do before changing focus or detaching your camera are flats. Bias and darks can come from a previously made library.

[ardbeg74]

Hi Russe,

Thanks for that mate. Got some flats made up last night, used the laptop with a blank text editor page as the light source. Also got 60 15sec subs, darks. got 60 bias as well.

Didnt have time to play with the data last night, thats something for the weekend. I also remembered to set the camera to raw+jpg... so the calibration frames might actually do something useful this time ( Tuesday nights M-42 shot in jpg was pretty orange and suffered from noise and obviously the vignetting which made it hard to balance )

Fingers crossed last nights image will be a big improvement. ( or likely provide another "learning experience"   )

Thanks for your great advice.

All the best

Mark

[crimpshrine]

If you have a laptop install EOS Utility and you can set it to take however many pics you want at whatever length.

[ardbeg74]

I'll download that and have a play with it on Saturday afternoon. Seems that it supports unlimited exposure time in bulb mode too, so thats going to save me a good £30 or £40 on a remote... I'll put that towards a polar scope. 

Nice one Crimpshrine, well spotted!! Ya just saved me time and money. 

All the best

Mark

[ardbeg74]

Hot off the press,  48 15 sec subs @ 1600 ISO and a quick muck around in PS. 

First step on a very long road..... thanks guys!!

Clear skies 

Mark

[Russe]

Good effort! Well done!!!