Focusing nightmare

[bish]

I thought I would put my 127  mak AZ out for half an hour tonight and  try to take a  snap of M42, after having a go at the Sun last week. An hour later and I still hadn't focused properly! Couldn't see anything on live view, and when I took a pic it was way out. In the end I had the idea to point at Sirius - which I could actually see on the live view. I focused as best I could but the air was very turbulent. Swung back round to M42 and was clouded out. After nearly 2 hours I had a gap in the clouds long enough to take this single 20 second exposure. Still not focused very well!  (There were a few more pics but M42 wasn't even in them..)

[redmoo]

Ever thought about a bahtinov mask? You can either buy one or make one yourself (I had a 127 mak and made my own). Website here:-

http://astrojargon.net/maskgen.aspx

Also, if you havn't already, stick a clothes peg on the focussing knob once you are close to the right focus. That gives you a lot better 'fine control' over the focus.

I guess you already know you are going to be limited to about 30 second subs with that scope though, and you are going to throw a lot away. Still, you can tag a few of the brighter DSO's!

[bish]

Ever thought about a bahtinov mask? You can either buy one or make one yourself (I had a 127 mak and made my own). Website here:-

http://astrojargon.net/maskgen.aspx

Also, if you havn't already, stick a clothes peg on the focussing knob once you are close to the right focus. That gives you a lot better 'fine control' over the focus.

I guess you already know you are going to be limited to about 30 second subs with that scope though, and you are going to throw a lot away. Still, you can tag a few of the brighter DSO's!

Thanks redmoo. I am going back out now, I will try the clothes peg trick. I will have a look at a bahtinov mask tomorrow.

[steppenwolf]

In the end I had the idea to point at Sirius - which I could actually see on the live view.

This approach is the key to achieving focus, forget the object you want to image for now, find the brightest object available (but not the Moon if it is up) and focus on that. Liveview does help but it can be very misleading as even the contrast setting of your display will try to fool you! If at all possible, take a laptop PC out with you and download the test focus images onto the PC so that you can scrutinise the focus on a big screen. A Bahtinov mask is a must and will transform the ease with which you can confirm focus. Once the bright star is in focus, everything else in the night sky will also be in focus.

The clothes peg sounds like a great idea for in creasing precision!

[davefrance]

To aid focusing you can set your ISO to the highest your camera will allow. This should increase visibility of stars in Live View (but don't forget to change it back afterwards). If you have 5x or 10x magnification in LV then use that as well. 

[Carina Lass]

Apt.

download it and use live viewx10 on sirius

Even without a Batinov mask it will give you a very close setting.

[bish]

Thanks for all of your replies. I'm definitely going to get a Batinov. I've been toying with the idea of an EQ5, and may  need a small guide scope too.

[redmoo]

Thanks for all of your replies. I'm definitely going to get a Batinov. I've been toying with the idea of an EQ5, and may  need a small guide scope too.

Is your end game imaging DSO's? If so, I would save up for a more sturdy mount (HEQ5 or the like). Also, I don't think that scope is the best for DSO's. I only say this because I was in exactly the same boat as you! I loved my 127 Mak. Gave me a great intro into astronomy. As soon as I started doing DSO's (much like the one you have posted above) I decided to go down the AP route. Have a look around at what people suggest for scopes (or more importantly mounts).

[bish]

Is your end game imaging DSO's? If so, I would save up for a more sturdy mount (HEQ5 or the like). Also, I don't think that scope is the best for DSO's. I only say this because I was in exactly the same boat as you! I loved my 127 Mak. Gave me a great intro into astronomy. As soon as I started doing DSO's (much like the one you have posted above) I decided to go down the AP route. Have a look around at what people suggest for scopes (or more importantly mounts).

Thanks for the advice. Yes DSO's are my thing for sure. I do get a bit impatient but also  have a nagging feeling that if I did get an EQ5 I would very soon be looking to an HEQ5. I'll just have to keep loading the piggy bank!

[redmoo]

Thanks for the advice. Yes DSO's are my thing for sure. I do get a bit impatient but also  have a nagging feeling that if I did get an EQ5 I would very soon be looking to an HEQ5. I'll just have to keep loading the piggy bank!

You can always go second hand. A lot of astronomers take really good care of their equipment. I got mine second hand with a 200p scope for 500 pound. Mint condition and tracks really nice. They do appear every now and again, but they are usually snapped up pretty fast!

[JR1987]

Are you sure your scope can achieve focus with a camera? I only ask because I came across very similar problems.. and found out my scope didn't have enough inward travel to actually achieve focus.. Barlow lenses work..but accurate tracking is near impossible! its ok for planetary stuff though 

[redmoo]

I had no problems reaching focus with a DSLR and a 127 mak. I did have a low profile T ring adapter though, so it is a valid point made above! 

But yeah, when you are relying on ALT/AZ mount to just 'track', it does have a mind of its own!

[peroni]

Thanks for all of your replies. I'm definitely going to get a Batinov. I've been toying with the idea of an EQ5, and may  need a small guide scope too.

You can download and print a template for the Bahtinov mask. Just print to A4 paper and then stick on some card to cut out. I fixed the card to an embroidery hoop (99p amazon special) and hey presto. A cheap Bahtinov mask that will do you proud.

[Carina Lass]

I used the back cover from an a4 resume folder.

It's about two years old now and still perfect

[frugal]

Thanks for the advice. Yes DSO's are my thing for sure. I do get a bit impatient but also  have a nagging feeling that if I did get an EQ5 I would very soon be looking to an HEQ5. I'll just have to keep loading the piggy bank!

The general recommendation for astrophotography is that the HEQ5 is the minimum mount in order to get a good number of successful images.