Jm1973

48 minutes ago, Budgie1 said:

I used a Celestron 9x50 finder for guiding and with that I had to remove the locking ring from the finder scope tube to be able to get enough travel on the front lens to focus. Just unscrew the front lens from the tube, then the locking ring and screw the lens back on.

I was using the Astro Essentials Sky-Watcher 9x50 Finder to C Adapter with ZWO ASI120MM Mini.

It means you can't lock the focus but I found it doesn't really move due to the thick grease on the threads.

Hi Budgie, thanks for the detailed reply. That sounds like it could do the trick. I will try it tomorrow assuming the clear weather persists.

Many thanks.

Thinking about it, if I'm screwing in the front part of the finderscope then that should mean I am shortening the focal length. So I think that means I need more inward travel. Does this mean I'm looking at cutting down the finderscope tube?

Hi. I've been imaging for about 5 months or so now, and getting along ok unguided so far. I can get 3 minutes subs without too much hassle.

However, quite often I have a lot of what seems to be 'walking' noise. I have bought a GPCAM2 and adaptor and had planned to use it with my Skywatcher 9x50 finderscope to autoguide, partly so I can dither and partly to have the chance of longer exposures.

However, I have been unable to get it to focus. I can get a bright star in view, but it is very large and diffuse. I can bring it towards focus to a point by screwing the two front parts of the finderscope clockwise, but when they are tightened as far as they can go inwards, the star is still very much out of focus - by what seems to be quite a long way. 

I am still a bit clueless about focusing. Does this mean I need more backwards travel, ie. an extender or spacer of some kind, or do I need to look into cutting down the finderscope tube? Or something else?

If anyone has come across this before and has any helpful suggestions, I would be very grateful.

So I've been doing a bit of research and I think I've found out what's going on...

Firstly it's not just that the focal point is quite far forward, meaning that the addition of the rotator effectively stops me from being able to achieve focus. Also there is a lot of coma and other distortion, which there shouldn't be as I am using the dedicated 0.85 reducer.

I have discovered that the sensor of the camera should be 55mm back from the reducer. I measured and mine is something like 100mm back. When I bought this it came with an adaptor which connected the reducer to my Canon 450D. However, it is not the M48 to EOS adaptor that is sold by FLO, it is one of these:

Obviously this adds way too much backward spacing for the reducer to work, and also pushes the camera further back meaning it has to come further forward to achieve focus, if I am correct. This would seem to be the source of both my issues - focus and field distortion.

I am going to purchase the Astro Essentials M48 to Canon EOs adaptor and see if that sorts things out.

Sadly I sold the rotator when I thought I couldn;t use it, and will probably have to buy another one now. Ah well.

7 minutes ago, scitmon said:

Yes, where you would normally screw your reducer onto the draw tube, you screw this adapter on instead.  Then the t nose slides into the  focuser like an EP would.

Great. That sounds like it will do the trick.

/puts hacksaw away

6 minutes ago, John said:

You are correct - when focusing on closer targets, the focuser needs to move further outwards.

 

Thanks. Thought I was going mad for a minute then.

9 minutes ago, SamAndrew said:

What are you focusing on during the day? the focus position should be further out when focusing at infinity so you might be ok.

I'm focusing on the roof of a building about half a mile away. I thought it was the other way around though? ie. it's further in when focusing to infinity. I am probably wrong.

30 minutes ago, scitmon said:

https://www.firstlightoptics.com/adapters/astro-essentials-adapter-for-sky-watcher-focal-reducers.html might work?  I successfully use this with the stock focuser, reducer and a dslr.

Aha! This looks interesting. So this fits in place of the stock connector on the 0.85 reducer? And enables rotation?

Hi everyone. I need to ask for some advice.

I recently bought an Evostar 80ED DS Pro, with the x0.85 dedicated flattener/reducer. It is fitted with a Moonlite CF focuser and Moonlite stepper motor.

I haven't had chance to use it yet due to weather, but I have taken it into the garden during the day and tested focus with ny DSLR attached, and I can achieve focus at about 2300 steps out from 0. 

So far so good.

However I also just bought one of the dedicated Evostar 80ED rotators from FLO. I fitted it and tested again during the day, and now I cannot get enough inward travel on the focuser to achieve focus.

Do I have any options to enable me to get focus with the rotator? I don't really want to be cutting down the OTA or anything.

Or do I have any other options for rotating the DSLR? I suppose I could turn the OTA in the tube rings to assist in framing, but I was hoping for something more accurate and less of a faff.

If anyone had any experience with this, or any ideas generally I would be very grateful.

12 hours ago, PeterCPC said:

In that case I would go with the Optolong L-extreme (if you can source one).

They are currently in stock at widescreen centre.

2 minutes ago, tooth_dr said:

100% tighten then enough so that it moves with the knob but not too easily.

 

Good info here:

 

Great. I'll take a look.

12 minutes ago, tooth_dr said:

I’m a big advocate of the standard focusers on my SW scopes.

I wouldn’t recommend removing the focuser, rather just remove the drawtube and check for even wear along the flat part. Then tighten up the screws to minimise movement of the drawtube. I do mine up really quite tight.  I have 1.8kg of kit on mine, so a DSLR shouldn’t be an issue.

As wulfrun suggests, you might not need to lock it, provided the tension is good.

 

 

To be honest I haven't even tried tightening the screws yet. It may be that that would be enough.

Thanks.

10 minutes ago, wulfrun said:

I have a couple of suggestions, which may or may not be useful. First one, do you actually need to lock the focus or is there enough friction to leave it unlocked? Second, try and figure if the lock moves focus by a consistent amount and which way. Mis-focus to that extent then lock to bring it back to correct. I agree further action is needed but this might give you a working stop-gap.

Yeah, it defintely needs locking. I attach a DSLR and if I don;t lock it goes out of focus during the session.

I think it might be a consistent thing. I need to run some tests when I'm not imaging and so not under pressure.

Thanks.

Maybe the OTA is put on slightly differently and the weight distribution affects the PA slightly?

That sounds like good advice. Thank you.

Hi everyone. I have a skywatcher 200p with the standard focuser. I have an issue where I stick my dslr on, take photos while slowly adjusting the focus wheel until it is in focus. Then when I tighten the lock screw, to lock the focus wheel, it knocks the focus off a bit. And I have to untighten the lock screw and start again. It's very hit and miss and it can take me half the evening to get focus locked, and sometimes I can;t do it at all.

Is there anything I can do to adjmust it so that when I tighten the lock screw, it doesn't affect the current focus?

Thanks!

2 minutes ago, Phillyo said:

I would think so yes. The only way to find out is to run some tests for your sky. You could always try using the sensor analysis inside Sharpcap software? It'll cost you £10 for the year but it's fantastic and will tell you what exposure lengths to use for optimal results.

I've actually got SharpCap pro, as I use their PA tool. I'll take a look at the sensor analysis. Thanks.

2 minutes ago, Phillyo said:

Guiding is absolutely worth doing, as pointed out above you can dither which is always great. The l-extreme is a dual narrowband filter for Ha and Oiii which will work well with your DSLR (although your Ha will be limited due to the IR block inside a DSLR) but only on emission type objects, not galaxies or reflection type objects. 5min should be plenty and you can always up the ISO a little bit if needs be. 

The DSLR has had the rear filter removal mod (not the full spectrum) so should be ok for picking up Ha. 

Do you think 5 mins will be long enough to pick up enough signal when using the l-extreme? If so that would be good.

1 minute ago, Ouroboros said:

I find 300s (5 mins) guided in Bortle class 3 at 400ISO for my 460D is about optimum. I could run for longer but tend not to as the chance of wind shake  or satellites ruining the shot increase. I hardly ever image now under the Bortle class 5 skies of Oxfordshire but I seem to recall that 2 to 3 minutes was about the limit. That’s not much more than you’re getting unguided, which incidentally is pretty good I reckon. But guiding is still worthwhile because you can dither and thus avoid taking darks if you want to. 

I should have added I am intending to use the Optolong l-extreme filter to cut down on the LP and skyglow, so should be able to get longer exposures without blowing out the histogram.

12 minutes ago, Phillyo said:

What DSLR are you using and why do you think going for the 'longest exposures you can' is a good thing? Not a dig, but a genuine question. The reason I ask is because your camera uses a CMOS sensor, not a CCD sensor. Once you have exposed long enough to get above the noise floor, the limiting factor for sub length is likely to be your light pollution levels. I would assume that Bristol LP isn't amazing so exposing for longer won't get you any more detail, just more light pollution. I would much rather shoot 100 x 2min subs than 2 x 100min subs. The longer subs also means more data lost due to aeroplanes, satellites, wind movement, bad guiding etc. If you take 2 subs at 100min and one of them is rubbish, you've lost 100min of data. If you take 100 subs at 2min and even 10 of them are rubbish, you've only lost 20min of data. Plus, with a lot of subs stacked together you can use an average combination method to remove satellite trails anyway.

Try not to get into the mind set that longer is always better. More data is always better sure but not always longer, not unless you're imaging from a bortle 1 zone of course  

Well at the moment my exposures are getting swamped by light pollution. For a 2 minute exposure I have to keep my ISO down to 400, otherwise the histogram is too far to the right, and that is with no moon. If the moon is prominent then I have to keep them shorter than that. I'm in a Bortle 6 with LED streetlights, and I am fairly close to shopping centres etc, so a fair amount of LP. By the time I have got rid of the LP my images are pretty noisy.

My attempted solution to this is to buy an l-extreme filter. From what I've read, this will cut down on the LP pretty well, but will require much longer subs. Hence the need to start auto-guiding.

1 hour ago, geordie85 said:

It really all depends on balance, polar alignment and most importantly the wind. 

I used to use the same set up and have achieved 30 minute subs but the slightest blow would ruin my subs due to the lightweight mount and the 200p acting like a sail.

Ah, I see. I guess then it is striking a compromise between getting the longest exposures you can, and keeping them short enough so they don't all get ruined by wind.

If I could get 5 or 10 mins I'd be happy to be honest. I might invest in a couple of windbreakers. I've got one in the shed that I never use...

Hi. At the moment I am using an EQ5 Pro Goto Synscan mount with a Skywatcher 200P and DSLR. I am getting 120 second unguided subs when I get decent polar alignment.

I've just bought a GPCAM2 and an adaptor, and I have fitted it to my 9x50 finderscope (to save weight). I control the mount and camera via a laptop already, and I will be using PHD2 to do the guiding.

My question is, what sort of exposure times can i realistically expect to get with the addition of autoguiding, with my current setup?

Thanks in advance for any insights. 

57 minutes ago, The Admiral said:

I'm not sure it will be worth it 😉. None of the sites are very accurate, and they often disagree with each other! Even disagree with the weather I've actually got 😀.

Ian

Yes, indeed. Clear outside will often be completely wrong even an hour ahead. Not quite sure how it manages that.

On 07/12/2020 at 15:37, Ade Turner said:

Everything seems absolutely fine. The handset initialises and goes through its usual lat-long, time and date inputs, and the motors respond as expected. Beyond that I can’t really check built-in alignment routines. 
Thanks for your help - hopefully all will work smoothly once I get hold of the right cable 👍

This is the one I use.

https://www.amazon.co.uk/gp/product/B085WT9VZ6/ref=afx_dp_prime_egress?ie=UTF8&fpl=fresh

2 hours ago, Quatermass said:

Good to hear from you again yes I really loved being part of this forum all those years ago and remember doing all this to get a guiding sytem set up. For now I am happy enough to start again with just the eq5 200p and the dual axis kit with the 450d its fun to use this simple set up. But I have no doubt that getting guiding set up really helps get better subs so will be looking to go that route again but this time I will be buying a good camera for guiding as the webcam was ok but not great.

 

I recently bought a USB2 GPCAM2 that I intend to use for guiding at some point. I'm going to try to use the existing 9x50 finderscope, which I think should work.