Dirft Align Issues

[pshepp1890]

Hey everyone, my first post here

Ive started doing drift alignment in order to get my scope properly aligned in my back garden so i can do some imaging. Im getting an auto guider soon but just want help in the mean time.

So i start of with a star in the south which i can align perfectly. Stays center for over 10 min without the slightest bit of movement, perfect

I then move onto a star on the western side which i then start to get problems. The star drifted slightly north so i adjusted everything until it stayed within the north/south cross hairs of my eyepiece. Problem i have is that the star still moves within the east/west cross hairs. I went back and checked on my southern star and that didnt move for over 10 min again. Went back to the western star which north/south did not move, stayed dead center for over 10 min but east to best it was most of the way off the eyepiece after only around 3 or 4 min.

What is the problem here? Could it be that the mount is not tracking fast enough?

All help needed if possible please guys and gals. Ive spent alot of money on this (for whats alot of money for me lol) and really want to get some good images.

Thanks all, Paul.

[Davey-T]

Hi Paul, and welcome to SGL, you've come to the right place for advice, not necessarily all correct

It's a good idea to try to understand what you're trying to achieve and how rather than just following instructions.

When drift aligning you're only setting the north / south drift and not worrying about east / west.

What eyepiece are you using, you really need a graduated / illuminated eyepiece and no more than 12mm 

Which mount do you have, you should / may be able to alter the tracking rate.

[pshepp1890]

I have  a 12mm illuminated cross hair eyepiece and i have an eq5 mount. 

Surely if the star is moving regardless of direction in the crosshair eyepiece, doesnt that still mean that i will be getting "star trail" in my images if im looking at something on the western or eastern horizon?

 

thanks for your quick reply by the way  that was fast  

[pshepp1890]

Also looking at the tracking rate on the synscan handset, it says 0.5x ? is that right? surely it need to be at 1x? 

[Davey-T]

Drift aligning is to aim the RA axis as accurately as possible at the NCP, remembering that ultimately you're limited by the engineering quality of the mount.
Mass produced mounts are by definition very variable as some folks have excellent results out of the box and others have a real struggle.

If the mount is not keeping pace with the stars or getting ahead of them no amount of PA ing will fix this which is where guiding comes in.

Dave

You can experiment with tracking rate

 

[pshepp1890]

Could it be that the mount is not getting enough power? or that its got too much weight on it? its perfectly balanced. Its only a 150 pds with a Nikon D810a dslr so cant really see weight being an issue.

Gone completely through the settings and its the auto guider speed thats at 0.5x so thats not the issue as im not using an auto guider. 

The tracking rate is set to Sidereal rate.

 

thanks again for your help, really want to get this sorted.

[Dr_Ju_ju]

Hi Paul,

Welcome to the Lounge...   You don't say what mount you're using with the 150pds, If its either and EQ3 or EQ5, then you may well have problems tracking, without using guiding, as you are pushing the capabilities of these mounts to their limits... 

 

[Davey-T]

Have you actually tried taking any pic's yet ?

Your scope has a 650mm focal length I think so at prime focus it will not show the movement as much as a 12mm eyepiece.

Once you get guiding PHD will tell you the actual speed it's tracking at.

Dave

[pshepp1890]

Its an eq5 that im using. So would an autoguider resolve this regardless. Again mentioned at the top i dont have alot of funds to put at this so im thinking of getting a st80 scope with the skywatcher synguider to work as my auto guider.

Would this be a definite resolution? If so its worth the extra £300.

[pshepp1890]

1 minute ago, Davey-T said:

Have you actually tried taking any pic's yet ?

Your scope has a 650mm focal length I think so at prime focus it will not show the movement as much as a 12mm eyepiece.

Once you get guiding PHD will tell you the actual speed it's tracking at.

Dave

Its a 750 mm focal and ive not taken any pics as of yet mate as  the movement east/west is so bad i probably couldnt even do a 30sec exposure without having star trails

[Davey-T]

Wouldn't recommend the Synguider, better of using PHD and guide camera, ST80 is fine, I used one for a few years.

Dave

[pshepp1890]

If money would push to a guide camera i would but it also means i would have to get a laptop so now id be talking in the £1000s just to get guiding lol thats why i was looking at the synguider as its relitavly cheaper and suits my needs slightly better.... Possibly lol

[Davey-T]

3 minutes ago, pshepp1890 said:

Its a 750 mm focal and ive not taken any pics as of yet mate as  the movement east/west is so bad i probably couldnt even do a 30sec exposure without having star trails

I'd defo jump in and try a few images regardless, you have to start somewhere

Then keep your images to chart your progress.

Dave

[pshepp1890]

Ive managed 2 photos so far when Orion was due south and earlier on when pleiades was due south. Everything south or north is perfectly fine. Its just east/west which i guess thats where stars are moving at their most as they are the furthest away from any celestial pole. 

[Dr_Ju_ju]

getting an ST80 would only make the mount capabilities even worse, du to the increased weight. You would be better off getting a modified guider scope..

 

As you have a Synscan handset, after you have done polar alignment, have you then done a 3 star alignment ?  if so when slewing to a new target, does it get there ?  if not do the alignment again...

I can do 3 min unguided subs on my EQ3 & 150P\Canon 600, so it should be possible.

 

[pshepp1890]

3 minutes ago, Dr_Ju_ju said:

getting an ST80 would only make the mount capabilities even worse, du to the increased weight. You would be better off getting a modified guider scope..

 

As you have a Synscan handset, after you have done polar alignment, have you then done a 3 star alignment ?  if so when slewing to a new target, does it get there ?  if not do the alignment again...

I can do 3 min unguided subs on my EQ3 & 150P\Canon 600, so it should be possible.

 

I do 3 star alignment to get set up then another 3 star once everything has been finalized right before imaging. It hits every object first time everytime without fail.  Anything on the north or south horizon is not affected at all, just objects that are on the eastern or western horizon which really makes me think its a tracking issue. 

[pshepp1890]

Can i just say at this point too that you guys are awsome. Nowhere have i ever had so much help and response like this so really, thank you guys. :D:D:D:D 

[Davey-T]

As you quickly realise astro imaging is a money pit, to get the images that you see on some of the posts may mean spending tens of thousands of pounds and still no guarantee it will work.

If you want to take wide field images then £300.00 would be better spent on a SW Star Adventurer rather than spend hours trying to achieve something that is beyond your equipments capabilities

To achieve good quality close up DSO images requires a minimum of HEQ5 PRO then you'l want a CCD camera and filter wheel and the list goes on.

We are not blessed with many clear nights so they are better spent capturing something rather than wasting them trying to achieve the impossible however if you like the challenge then persevere, I've spent countless hours trying to get things to work properly but it's never really bothered me if I'm out under the stars.

Just re reading this it sounds a bit negative and discouraging but please don't give up, it's a really rewarding and worthwhile hobby

Dave

 

[Physopto]

Dave and the others here are quite correct. It can be a money pit. Not just imaging but any form of astronomy. Once the bug bites you can spend enormous amounts, BUT that is not necessary in reality. We do so because the bug has bitten.

You are best advised to get some images first, then after you have several under your belt you can decide if you want to take it any further. Many of us get few images, but enjoy the prospect of fixing something (even if it ain't broke   ). Others get "so so" images and are happy that they got something at all. Others like Olly, get fantastic images and that is not down to luck, but persistence and knowledge of what they are doing. You can also add PRACTICE to that. We need lots of practice. I would worry about the finer details after you have some experience of actual imaging first. You will learn and pick up things for years to come. It cannot be learned all in the first few minutes, so to speak. Your knowledge of the equipment you presently have will take some time to accumulate. So go for it get imaging. OK in between the clouds.

Derek

 

 

[pshepp1890]

Ive came to realise that its a very expensive hobby but i love it. I'm a huge perfectionist (incase you cant tell) lol I really want to get some beautiful images. When the money permits, i will look at upgrading to a eq6 with maybe a 200 pds and autoguider system but at the moment thats well out of my range. 

The issue i have with drift align, i dont think is a case of "not getting it as i want" so to speak, something is definitely not right. A star on the south horizon staying dead still but on the west or east it drifts like mad. I change the altitude but thats not the issue as the star does not drift north/south so the altitude is spot on. Really dont know whats going on. Like i mentioned before its to the point where i couldn't even take a 30 second exposure without huge amounts of star trails.

I live in the new forest so i have the perfect setup around me, no light pollution so i really want to take advantage.

[Davey-T]

Probably is just tracking too fast / slow, difficult to measure without using laptop / software.

Does your illuminated eyepiece have a graduated reticle ? you can use it to measure how fast the mount is moving, involves a bit of maths.

Dave

Here's an animated GIF of a mount that I had,unguided, perfectly polar aligned but not keeping up with the stars.

[pshepp1890]

It's just a standard red illuminated cross hair eyepiece. Nothing fancy. 

I mentioned before that il looking st the synguider with st80. Ofc this is going to add a little more weight but would that really be an issue if the synguider is telling the mount what to do to keep up and keep stars centred? I've filled the legs with sand and sealed them so stability is not and issue. In fact it's one of its strongest points now ? 

[Davey-T]

Good luck Paul, the good thing about astro equipment is there's always a ready market for used kit when you upgrade.

Dave

[kens]

6 hours ago, pshepp1890 said:

The issue i have with drift align, i dont think is a case of "not getting it as i want" so to speak, something is definitely not right. A star on the south horizon staying dead still but on the west or east it drifts like mad. I change the altitude but thats not the issue as the star does not drift north/south so the altitude is spot on. Really dont know whats going on. Like i mentioned before its to the point where i couldn't even take a 30 second exposure without huge amounts of star trails.

This is an interesting conundrum Paul. Assuming you are drift aligning near the celestial equator (declination 0 deg) at both the meridian and the equator, the most likely cause of your problem is balance and/or overloading. Normally these would manifest around the meridian rather than the horizon though. As long as you are at dec 0 the tracking should be the same, apart from some refraction effect which is negligible unless you are right on the horizon. Dec 0 is the same distance from the pole regardless of whether you are pointing east, west or south (geographically)

One thing that draws my attention is that you drift align with the eyepiece and image with the camera. 

Now most problems people have with alignment and guiding are the most basic ones so the obvious question to ask is if you are rebalancing the scope after attaching the camera.

Another question is whether you are balancing in all three dimensions. That is, with the counterweight shaft horizontal:

1. Counterweights and OTA are in balance on the RA axis
2. With OTA horizonal it is in balance on the dec axis
3. With the OTA vertical it is rotated in the rings so that it is still in balance on the dec axis

You may already be doing all the above and I know you said your balance is perfect, but when doing a blind analysis I find its best to check everything.

It would be useful to know just how much RA drift you are getting on your images. Get one of your 30 second images, zoom in on a star trail and count how many pixels long the trails are. You can calculate your pixel scale at http://www.wilmslowastro.com/software/formulae.htm to work out how many arc-seconds you are drifting. 

Other possible causes of your RA drift are:

• periodic error, which could be large on that mount but should show up regardless of orientation. Autoguiding can help here.
• gear mesh: either too loose or binding - this is made worse if your setup is not balanced
• faulty cable to the drive motor. A dodgy wire or loose connections might only show up on extreme orientations when the cable is stretched

and more...

By the way, you should list your equipment in your signature to help with any troubleshooting - it's under your Account Settings

[Davey-T]

3 hours ago, pshepp1890 said:

It's just a standard red illuminated cross hair eyepiece. Nothing fancy. 

I mentioned before that il looking st the synguider with st80. Ofc this is going to add a little more weight but would that really be an issue if the synguider is telling the mount what to do to keep up and keep stars centred? I've filled the legs with sand and sealed them so stability is not and issue. In fact it's one of its strongest points now ? 

If the mount is running too slowly to keep up the guider won't speed it up.

Dave