Frustrating evening trying to frame object

[kirkster501]

..between dodging cloud that is.....

First light of my RC8 tonight and also my IDAS LP filter.

I was trying to image M81 - my fave object. No matter what I did I could not get it into the FoV of the camera. This is bizarre. With LiveView on I could find surrounding stars OK like Dubhe, Kochab and a few of less bright stars North of M81. I used EQMod to centre these with an 22mm EP first. After getting focus with my Bhat Mask I went round each one again with Liveview with my DSLR at Prime Focus and calibrated the position of each star so i got it bang center.

Right me thinks lets party..... So I slew over to M81. I take several subs. No M81 on them. I repeat the above procedure (that I use on my ED80 all the time btw) no luck. I think I caught a smidge of something fuzzy on one occasion but probably NGC3077, was nit the distinctive M81.

Anyone think what i might be doing wrong? On a longer FL scope like the RC8 I take it as read that more exposure is required to see something. But I was waiting for two minutes or so on my test framing subs- I'd expect to see something fuzzy after that time, even on a longer focal length. Maybe the LP filter is adding to the exposure required as well - a double whammy?

Frustrating might indeed. Came away with not a sausage n the can after five hours and i was expecting to be showing off my brilliant M81 now All part of the fun though! And yes I did make the mistake of leaving the Bhat Mask on once as well...

Appreciate a steer please guys?

Rgds, Steve

[kirkster501]

I meant to say, I was still working hard at this trying to bottom out the issue when it clouded over and looked like it was going to stay like that so i packed up. Naturally, as soon as all the stuff was back in the garage it cleared up. So, I started to set up again. in my eagerness to bottom this issue out. Was half way through doing so and it clouded over again - wit a little light drizzle thrown in. So I finally packed up and came in. Now of course its clear. As I said elsewhere, my kit is like the Hokey-Cokey tonight, three times in and out being set up and taken down.

[kirkster501]

Well, actually I did get M81 but since I was not guiding yet (first night last night with this scope and dont have the mounting hardware yet) and I am working at a longer focal length I got the core of M81 and took this to be a whole other galaxy - similar to my work flow on my ED80 - and now notice on closer inspection in the light of day that I do indeed have the outer spiral arms of M81 but that THEY FILL THE FRAME NEARLY!!!!! I was not prepared for the MUCH larger image scale of the galaxy on the RC8 scope compared to the ED80 and this is what threw me. I was using three minute exposures and I can now appreciate the likes of what Olly says in that guiding at 1800mm takes some doing.

I think also that the wide field view of the ED80 has taught me bad habits..... I can do my alignment with the ED80 roughly and can normally get my subject framed since the FoV is so wide. However, when imaging at higher scale and longer FL the scope must be MUCH more accurately pointed and this is where i went wrong last night i think.

Early days however and Rome was not builit in a day. Will keep at it. I think this scope has great potenetial for large image scale subjects such as small galaxies, planetary nebulae and globuars. I need to get the guiding scope sorted out first though since even a footstep near the scope vibrates it enough to spoil the sub.

Steve

[russellhq]

Have a look at the Astro Tortilla thread in the software section. I use this for plate solving and slewing to targets and it works a treat (in combination with ATP). Normally all it takes is: set-up mount, rough polar align, slew to target, run AT and plate solve where I am, AT then sends a sync command to EQMOD to tell it where I really am, I then slew to target again and take a 30s exposure at high ISO. From there it's usually on target and I only need to do minor adjustments in live view to get framed. (AT also has a frame option where you give it an image and it'll slew, capture and plate solve until it's got it centred. Although I had trouble with this which I think was down to the backlash in my mount).

[Luke]

I think you'll be fine at 1800mm once you get used to it. I think I have similar focal length when I reduce my C11 to F6.3.

I do my alignment on three stars roughly in a triangle around the target using Live View (this is fun when using a Ha filter!...) and make sure they are all well on the same side of the meridian, the same side as the target.

When it doesn't work. it is usually caused by one of two things for me:

- i aligned on the wrong star (I blame tiredness!)

- one of the stars was the other side of the meridian

Hopefully you're well on the way now anyway. As you say, all part of the fun! :-o

[kirkster501]

......and make sure they are all well on the same side of the meridian, the same side as the target.

Thanks Luke/Russell.

So do you mean ensure all the alignment stars are, say, to the left or to the right of the object I intend to image? I thought, for no real reason really, that "surrounding" the object might have been better?

Another thought..... I only aligned the mount from stars in the vicinity of the imaging target So in the case of M81 all my alignment stars were within a few degrees of it. Perhaps that is not giving EQmod a big enough "surface" to get the sky in its brain and accurataley point the scope?

[kirkster501]

Wow, that AT plate solving software looks very powerful indeed ! I shall have a play with that tomorrow. Thanks for the pointer

[robin-m]

For me the best feature of AT is you can save a quick sub of your FOV from one night and then load it into AT another night and it will take you to within a few pixels of where you were. It saves a huge amount of time trying to line yourself up again.

[kirkster501]

A very good reason indeed robin-m. I am going to look into this later on. It looks pretty amazing.

[jezhughes]

Try a 1 star align on a star near 81, anything in the dipper i guess? I had this same issue the other day but realised that i hadn't aligned on anything close to the target. if you're imaging you sometimes only need a 1 star align and if you do this close to your target, slewing accurately to it becomes easier.

Good luck next time. the core of 81 *should* come up in your preview, even with a hard LP

[kirkster501]

One of the difficulties is that when learning stuff like this with new kit and techniques, we have so few clear nights of late its nigh on impossible..... Makes me want to put the new gear to one side and get something in the can with equipment I DO understand!

[jezhughes]

know that feeling very well after investing a small fortune in the last 6 months and only getting 2 nights of clear skies in. That's what i bought an OSC in the end and small frac. stripped things down and taking it step by step. the learning curve is steep enough without the 3 month gaps in practice

[Jessun]

This little program is fun to play around with to see what FOV you'll have with different scopes and cameras. Maybe you've seen it, but here it is:

http://www.newastro.com/book_new/camera_app.php

/Jesper

[Luke]

Sorry, I did mean surrounding the object, ideally.

What I make sure is that the target and all three alignment stars are all on the same side of the Meridian (i.e. all on the east side or all on the west side of the imaginary line from North to South - whichever side the target happens to be on at the time).

Another thing I do is to use crosshairs in the live view of Backyard EOS to make sure the star is really central. I used to use Canon Utility and guess it, but things are more accurate since using the crosshairs.

I find that if one of the stars is over the other side of the Meridian, the goto is not very accurate. It could be that it would be fine if I changed some setting or other, this is just what seems to work for me! And it might be bad habit but when something seems to work I try and stick with it, as there seem to be so many things that can go wrong with an imaging rig!!

My latest fumble was thinking I was taking an hour of darks, only to find out I had taken zero when I came back an hour later. I'd left the camera on some setting or other, I think it was A/V or something like that, which I use when taking flats. I forgot to put it back on bulb before taking the darks! I never seem to run out of new things to go wrong!! :-o The joys of imaging!

So do you mean ensure all the alignment stars are, say, to the left or to the right of the object I intend to image? I thought, for no real reason really, that "surrounding" the object might have been better?

[ollypenrice]

What I would do is a normal alignment on a fairly near star, something in Ursa Major. Then I'd do a slew to a star closer to the target like 23UM. I'd re-synch on that and then go to the the galaxy. If you can't see it it will then surely bececause the sky isn't allowing it that night.

This process of 'laying off' on a nearby star is very good because if your slew to the star doesn't find it then you have an alignment problem.

Olly