Longest Exposure with Synscan

[scottphillips]

Tested out the accuracy of my polar alignment the other day on my new 127mak eq-5 and it tracked jupiter perfectly for a good 20minutes without any adjustments and even through the 10mm it was centred and tracked smoothly !!

Just got my canon 450d and t-ring and adapter and was wondering what the longest exposures I could achieve for DSO's like Andromeda which I plan to image first ??

[Tinker1947]

Just try it and see, start at ISO 800 and 30 seconds then go up in 15 second jumps, i suspect you may get a couple of minutes, if the camera has Liveview zoom in and check how round the stars look each time.......

[philj]

Agree with tinker, try it and see, although due to the f12 fl of the mak you wont get long before trailing, I suspect around 30 seconds or 60 if you are really lucky with getting spot on pa.

[scottphillips]

Great thanks guys !! Will a focal reducer benefit me ? Also so I can give it a try, how many 30's exposures and what settings do I need to take an acceptable image of andromeda ? And yes the camera has live view

[Tinker1947]

I agree with philj, i never really gave the FL much consideration, a 130 P-DS would be a lot better and @ £159 from FLO not to bad on the wallet.....

[lensman57]

Tested out the accuracy of my polar alignment the other day on my new 127mak eq-5 and it tracked jupiter perfectly for a good 20minutes without any adjustments and even through the 10mm it was centred and tracked smoothly !!

Just got my canon 450d and t-ring and adapter and was wondering what the longest exposures I could achieve for DSO's like Andromeda which I plan to image first ??

About 30~60s unguided. Tracking a planet visually is very different to tracking a point source of light for imaging. Even  with excellent PA and a wide scope you'd be lucky to hit 180s unguided.

A.G

[happy-kat]

First I would see how many seconds you can get before unacceptable star trailing, then with that exposure length look at the iso setting want to aim about 70% on the histogram.

Make sure in camera noise reduction is turned off if you are going to take darks too.

[tingting44]

70% on the histogram.

70%? ive all ways aimed for 25% 

when i shot M31 i had an ISO of 800 with 10min subs and my histo was just under 25%

here is one of my single subs at the above conditions....

M31  (single RAW 10min sub - NO PROCESSING) by tingting44, on Flickr

[scottphillips]

Ok I'll give say 10 x 20 second exposures on andromeda and see how it comes out !!

Another question, I have seen in previous threads about subs and darks etc and not sure what they are or how to take them using my DSLR ??

[Scott]

I agree with philj, i never really gave the FL much consideration, a 130 P-DS would be a lot better and @ £159 from FLO not to bad on the wallet.....

130 pds is rubbish... have you see the dross uranium 235 is putting out

http://stargazerslounge.com/topic/239003-flame-to-sword-update-130pds/?p=2591175

Sorry, got sidetracked...the mak is quite a long fl but hey,it won't cost you anything to give it a go...I might be inclined to bump up the iso to 1600 with exposures only 30-60 sec long.

As tinker147 has rightly pointed out, the 130 pds is showing itself to be an incredible imaging scope in the handsof the compitent and are very reasonably priced

[happy-kat]

70%? ive all ways aimed for 25%

I guess I use my left to right differently :-)

[wxsatuser]

With a DSLR your main aim is to get the histogram away from the lefthand side.

The histogram runs left to right and the first line from the left in Canons is 20%.

The 20% mark is a good starting point for the correct exposure for your sky conditions.

As Martin, I normally aim for 25% but you can push that to 40%, the further you push to the right

the more likely it will be harder to seperate the faint stuff from the sky.

There is no harm in experimenting with your camera to find the sweet spot but I prefer not to waste good

imaging time and just get that histogram peak somewhere in the range of 20 to 40%

[happy-kat]

Ah that explains I was reading opposite but same outcome just confusing for others