Roy Foreman

Just to add my two penny worth,  I've owned an OO 8" reflector for about 10 years. Optics are first rate and still in pristine condition. Mechanics leave a lot to be desired though. The primary mirror adjustments are very primitive and awkward, and the tube diameter is a bit on the small side - there should be something like an inch between mirror and tube to allow air currents to spiral up clear of the light path - mine has less than half that. And OO tend to size their secondary mirrors on the small side. Ok for visual but for imaging you are going to want a couple of sizes larger - which they will do for you.

I recently used SharpCap to polar align my EQ6 and I have to say I was impressed by how quick and easy it was to do. As you probably know the software provides two methods of adjusting the PA. The first is by adjusting the mount until a highlighted star - later two parallel lines - coincide with each other. The second is by watching the RA and DEC offsets reduce in magnitude as you adjust the mount.  If using the latter method it is important that SharpCap knows your latitude and longitude for accurate results. I managed to get my PA down to 25 arc sec, and the reason I could not get better than this is because the adjustments on the EQ6 were just not fine enough to achieve any better, so it is a very sensitive procedure. Just mounting a scope on the mount can shift the alignment by a small amount, particularly if it is a big heavy OTA.

As for your star trails, if they are east-west then it is most likely down to periodic error, if at some other random direction then probably polar alignment.

Since doing my PA I haven't had a clear night to try it out. When I do I will report back and let you know my findings

Good luck and clear skies

Very nice and well done. Here in the UK we can only dream of such imaging targets !

I have been waiting over four months for a clear night with no clouds and no moon. According to my records 21st September 2020 was the last time I was able to do any deep sky work. I live in the southwest. Summer 2020 was, however, very productive, but it did mean waiting until 11.30 pm to start imaging !

Very nice shot. Clavius is my favourite crater. I always assumed a red filter was the one to use to minimise the effects of atmospheric turbulence, but your shot through a blue filter has worked really well.

Presumably a very tall one !!

It's one of the reasons I keep to short exposures, We actually had the first clear-ish night a couple of days ago, and it was a case of take a shot, wait for the cloud to pass, take another, wait for the next cloud etc. If you are doing 5-10 mins and that cloud comes when you're half way through .....

It;s good to know I'm not the only 'going slowly insane' astronomer around !!!

Yes I agree - using higher ISO is like turning up the brightness at time of capture rather than in processing. Never tried taking side by side images at ISO 200 and 6400 for the same duration and then processing each to see which reveals most detail / less noise.  When I get a chance I'll try it.  I've done it with 1600/6400 and the 6400 turned out less noisy. Can't show you the results of that because I since discarded the images as being below par.

To reply to the above few posts in one hit - firstly the D810a is not like a regular D810. The lowest ISO setting has been raised from 64 to 200, so the sweet spot is probably higher at something like 1600.  I seem to remember reading that somewhere. A 60 sec exposure at 1600 could probably be pushed to look like a 60 sec exposure at 6400 but I've never tried it. I have taken images of star clusters at ISO 200 and they can be pushed quite dramatically, but nebulae are not quite so forgiving.  Most modern cameras perform really well at high ISO's these days, and my personal preference is to keep exposures as short as possible to minimise tracking errors, atmospheric effects and the like.

In terms of total imaging time, to a certain extent, yes, 15 minutes of imaging at 6400 gives similar results as 60 minutes at 1600 - for  a single image. But, at 6400 you will need a minimum of 5 exposures to smooth out noise, whereas at 1600 you can get away with three.  So it's 75 minutes versus 3 hours !

I must stress that the above applies to the D810a, but I can't see why the same logic cannot be applied to other cameras.

Nice image of the heart nebula Joel, well done at ISO 200 !

My camera is a Nikon D810a and is designed for astrophotography, so I think nothing of using ISO 6400 on a regular basis. Other cameras may not work so efficiently at these high ISO's, but I would suggest most would give decent results at ISO 1600. The advantage of high ISO's is shorter exposure times, which is an advantage when making the most of short imaging windows in the weather, as I often have to.

Here is an example of an ISO 6400 image :-

There is a trade off with ISO settings. Low settings like 200 will give higher quality and can be pushed further during post processing to bring out details, but will require longer exposure times. Higher settings like 6400 will reduce your exposure times quite dramatically but will produce a lot more digital noise. Generally you can offset this but taking several identical shots and stacking them together (I usually take 5 or 7) in photoshop.

As a guide for the Pleiades, try 5 x 60 sec at ISO 6400 and see what you get.

Let us know how it turns out

I too am driven to despair with the weather. I have a brand new and very expensive RASA 11 that has been waiting 4 months to see first light. And it's still waiting. Sometimes I think 'why am I bothering with all this',  Then, when eventually the skies do clear, I know exactly why I bother - astronomy is in my blood and has been all my life. If it really is in your blood you will endure all the aggro alongside the pleasure you get from being under the stars.

As others have said, clear skies will return soon !

Thanks for the welcome Jeff !

I have seen the sun on occasions recently, but not clearly enough to consider looking at it through a solar scope - yes I have one too.

I keep a log of the night time weather - have done for several years - and here in West Somerset, the last time we had skies cloudless enough to consider deep sky imaging was 21st September 2020. That borders on unbelievable.

The forecast for tomorrow night, Saturday is for clear skies from 11pm until 3am. I shall be staying up to witness this incredibly rare celestial even, but I expect it will be clouded out as usual !

Roy

Thank you Dave - the warm welcome is much appreciated !

Thank you Nigella - yes there have been sunny days but no clear nights, great for your solar work ! Already done time looking at the RASA, now I need to make some modifications to it before first light. Those Losmandy rails top and bottom have just got to go. Really hate dovetail mountings on larger scopes, so I replace them with a setup that is much easier and safer to use.

So I'm not totally to blame then, you have contributed to the rubbish weather as well by getting a new scope. Please don't give up on Astronomy - although I know the feeling well !

You are right - the weather will improve one day. Good things are worth waiting for, as they say. Good luck with the new scope when it finally gets first light !

Thank you Les for your jovial response - made me laugh. I do get the feeling that bad weather seems to follow me around, so I suppose I must take some credit for it all. Having an observatory helps - I can be ready to go in 5 minutes if there is a break in the clouds, but we are not even getting that at the moment.

At least the spring and summer just gone provided many clear nights, it just meant staying up until 2am !!!

Thank you both for the warm welcome !

In times of prolonged cloudy weather I often cast my mind back to a holiday I had a couple of years ago in North Africa. It included a couple of nights in the Sahara Desert.

The skies there are to die for.  The stars, and the milky way, go right down to the horizon undiminished. It was so dark I could not see a hands length in front of me without a torch.

I had taken some rudimentary imaging equipment with me, but polar aligning was a problem. Here in the UK it's easy to find Polaris - it's the brightest star in that part of the sky. Not so in the desert. It was drowned out by all the other stars. Couldn't use the Plough to locate it - that was below the horizon !! Cassiopeia then.  Now which of those stars make up the familiar 'W' of Cassiopeia ? It wasn't easy to decide.

Didn't see a single cloud in the sky, day or night, the entire time I was there.

Oh well dream on Roy !

I have an EQ6 EQ/AZ which is very similar, and I totally agree with your sentiments. It will track unguided for 60 sec at 2m focal length (8" SCT) with very decent results.

Sad you had to part with yours - maybe one day you will own another one ?

Thanks to all who have replied and made me feel welcome !

Ah yes, I hadn't thought of that !

Bet there will be a lot of unwanted astro gear on the second hand market next year

Thanks for the welcome

Hi everyone at SGL

My name is Roy, I'm a new member, and I joined back in March 2020 but as yet haven't got round to posting anything. This, my first post, has been inspired by something close to the heart of all astronomers - the weather !

Now I know UK weather isn't great at the best of times, and it's taken a bit more of a hit over the last five years or so - at least in the south west. But for the last four months it has been exceptionally dire.

At the end of September 2020 I purchased a RASA 11 to add to my collection of optical paraphernalia. Its arrival inspired the heavens to dump record amounts of rain on the UK. Endless cloudy skies followed. There were two clear nights in October coinciding with full moon - no good for deep sky stuff. November offered up another clear night at the time of a 10 day old moon. No good either. The whole of December was totally clouded out (at night) and January has been the same so far.

I have been into astronomy for over 40 years and can't remember ever going so long without a celestial fix. The RASA has spent the first four months of its life standing in the corner of the observatory gathering dust, not photons,

It's not only telescopes that are smitten. A couple of months ago I got a pair of 20x80's (my first ever astro binos). Now you don't need clear skies to try binoculars, you can test them in daytime.  Their arrival heralded three days of thick fog - arrgghh !

I live on the edge of Exmoor which has some of the darkest skies in the country. Now it seems to have some of the cloudiest too.

My non astronomical friends just don't seem to appreciate my despair, hence the motivation to post this tale to a community of people who most definitely will !

I wish you all clear skies - with envy, of course !

Roy