M101 - first galaxy with 200PDS on HEQ5

[Apharov]

Here's my first galaxy image. 25 x 75s unguided @ ISO3200 with unmodded Canon 70D and Baader MPCC MkIII, with flats and darks. I first stacked with DSS but then moved to Nebulosity and got much better preserved and pleasant colours. Final processing in Lightroom.

I didn't get a really good balance on the RA axis since the HEQ5 counterweights are not quite enough for the scope + SkySurfer V RDF + 70D, but tracking was surprisingly good nonetheless. That tracking success was unfortunately not quite repeated last night, but that's another story

[Apharov]

..and again, a less compressed version can be seen at http://aapo.smugmug.com/Astro/i-4FZk5B3.

[GuillermoBarrancos]

Nice work! Well done!

[purdo]

Lovely image, you must be well pleased.

[Tommohawk]

Hey thats very nice! We were discussing alignment and tracking on another thread, so looks like you have that sorted!

You seem to have a lot of detail for subs of 75 secs. I had a go at M101 with my EQ3-2 but my efforts not so good. I used 90 sec subs, but had to chuck almost all due to horrendous periodic error. I now have HEQ5 which is much better. Have just fitted belt conversion which is nice but still have PE from the worm - I'm working on that and will do a report of some sort when time and skies allow!

[HumptyMoo]

Nice image, I was trying to view this one a few nights ago but couldn't find/see it, appreciate the post!

[Tommohawk]

Not sure why but I really struggled to locate M101 too. I think the star hopping path was less obvious than some. Have goto now though - bliss! Less time setting up and more time imaging.

[leemanley]

Great image, you must have some nice dark skies about you over there.

[Pete Presland]

a cracking image especially for un guided subs! you should be very pleased with it.

[Landy Dave]

Nice image. It’s good to see someone else using a 70D.

Why did you use ISO3200 as I have found the noise gets noticeably worse over ISO 2000?

[Apharov]

Thanks for the nice comments!

I've been doing the imaging some 50km north of Helsinki, so there's only relatively minor nearby light pollution. Last night the Milky Way was actually visible for some time

About the high ISO: the setup is not guided, so I'm pretty limited on sub length. I experimented with 120s @ ISO1600 and 60s @ ISO3200 and felt that I was left with a substantially higher keeper percentage with the shorter / higher ISO subs. Guiding is something that I'll probably add at some point, but with my current mobility and setup/teardown time limitations it's too heavy a solution.

[Apharov]

Hey thats very nice! We were discussing alignment and tracking on another thread, so looks like you have that sorted!

You seem to have a lot of detail for subs of 75 secs. I had a go at M101 with my EQ3-2 but my efforts not so good. I used 90 sec subs, but had to chuck almost all due to horrendous periodic error. I now have HEQ5 which is much better. Have just fitted belt conversion which is nice but still have PE from the worm - I'm working on that and will do a report of some sort when time and skies allow!

Last night my alignment seemed to be pretty accurate using the polar scope (verified with drift alignment), but the mount seems to have heavy periodic error. In drift alignment I got close to zero movement in the up/down directions, but lots of movement on the RA axis.

This brings me to the point: did you get an improvement in PE with the belt conversion or did it simply eliminate backlash? I seem to have heavy backlash in DEC, so I'll probably end up tuning the mount in near future anyway.

[Tommohawk]

This brings me to the point: did you get an improvement in PE with the belt conversion or did it simply eliminate backlash? I seem to have heavy backlash in DEC, so I'll probably end up tuning the mount in near future anyway.

The belt conversion is very nice, and probably eliminates PE and pretty much all backlash in the gears. However it hasnt fixed the PE problem overall. I get a distinct slow down/speed up about every 10.5 mins which is 1 worm revolution. When I get some clear sky I was going to test this in more detail, but I think its an eccentric or worn worm.

Unfortunately, because of uneven wear in the in the 132 tooth brass gear on which the worm works, if I adjust for minimal backlash, I get binding over a sector corresponding to about 45 degrees. So I have to adjust the worm to give some backlash to prevent binding in that sector. My impression is that backlash doesnt seem to alter much through one rev of the worm, but theres so much of this its hard to tell. I think if I could reduce the underlying backlash the PE might reduce - wishful thinking perhaps.

I have some thoughts on this, but I'm going to start another thread cos am at risk of hi-jacking this - see you there maybe!

Cheers Tom