Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

stargazine_ep28_banner.thumb.jpg.b94278254f44dd38f3f7ee896fe45525.jpg

Lee_P

Focus Control Current Position -- is this normal?

Recommended Posts

Hi SGL Wizards,

I'm using an ED-80 with HitecAstro DC Focus, and am controlling it via SGP Pro. I've got autofocus working well (hooray!) but notice that each night the Focus Control's Current Position number gets larger and larger. For example, a month or so ago it was around 9000 for focussed stars with a H-a filter. Tonight it's 12884. Is this normal? I'd expect the number to be absolute, i.e. always around the same number but with some slight variations given temperature and the like.

Thanks in advance,

 - Lee

Share this post


Link to post
Share on other sites
9 minutes ago, Lee_P said:

Hi SGL Wizards,

I'm using an ED-80 with HitecAstro DC Focus, and am controlling it via SGP Pro. I've got autofocus working well (hooray!) but notice that each night the Focus Control's Current Position number gets larger and larger. For example, a month or so ago it was around 9000 for focussed stars with a H-a filter. Tonight it's 12884. Is this normal? I'd expect the number to be absolute, i.e. always around the same number but with some slight variations given temperature and the like.

Thanks in advance,

 - Lee

This is a Hitec issue not SG Pro.  As the controller doesn't report its last position to SGP on start up, it just takes the last known position.  If your focuser moves when the power is off, this position doesn't change so it will be out, and if this is only a little bit, over time it will be cumulative.

If you use a Laskeside the calibration is within the unit, so it reports its actual position to SGP and doesn't have this issue, but the Hitec driver I think is a little more basic.

It doesn't really matter too much.  All you need to do is every now and then just do a re-zero on SGP so it knows what is fully in.

Edited by RayD
  • Like 1

Share this post


Link to post
Share on other sites
8 minutes ago, Lee_P said:

Ok, thanks for clearing that up.

One thing just to have a little check of Lee is if you are using a Crayford type focuser this could be indicating slip, so you may need to look at this and perhaps asjust the focuser (mechanically) to reduce slip.  Main thing is it isn't absolute, so SGP will just work from the start reading.

Edited by RayD
  • Like 1

Share this post


Link to post
Share on other sites

The Hitecastro DC focus, is for a 12v DC motor and not a stepper, so it wont be very accurate, as DC motors dont have repeatable position, or am i missing something...

Share this post


Link to post
Share on other sites
4 minutes ago, LightBucket said:

The Hitecastro DC focus, is for a 12v DC motor and not a stepper, so it wont be very accurate, as DC motors dont have repeatable position, or am i missing something...

Could be, but SGP still needs to know or assume the starting position, and if the focuser moves whilst the power is off then this doesn't change relative to the focuser.  I have the same issue with my Mount Hub Pro running on my Lakeside motor, which is a stepper.

Share this post


Link to post
Share on other sites

Yes, been looking into the mount hub pro, but the stepper controller leaves a lot to be desired, as it only works with full steps, and with some motors such as the feathertouch micro motors, this only equated to approx 750 steps per rev, and not enough for me... am supprised they haven’t upgraded the controller, i have also a pegasus motor and controller and that gives 8500 steps per rev which is superb...

sorry OP a little off topic.. :)

Share this post


Link to post
Share on other sites
11 minutes ago, LightBucket said:

Yes, been looking into the mount hub pro, but the stepper controller leaves a lot to be desired, as it only works with full steps, and with some motors such as the feathertouch micro motors, this only equated to approx 750 steps per rev, and not enough for me... am supprised they haven’t upgraded the controller, i have also a pegasus motor and controller and that gives 8500 steps per rev which is superb...

sorry OP a little off topic.. :)

Yes agreed, I have the Pegasus on my TS80 and it works absolutely fine.  I also have the Pegasus Hub Ultimate and the focus controller in that works really well.

Share this post


Link to post
Share on other sites
27 minutes ago, RayD said:

Yes agreed, I have the Pegasus on my TS80 and it works absolutely fine.  I also have the Pegasus Hub Ultimate and the focus controller in that works really well.

Have you tried the pegasus motor on the mount hub pro, if so how many steps per rev does that give, that info would be useful to me.. :)

Share this post


Link to post
Share on other sites
Just now, LightBucket said:

Have you tried the pegasus motor on the mount hub pro, if so how many steps per rev does that give, that info would be useful to me.. :)

I've not but I will be as I've just got an adaptor I've been waiting for for the TS so I'll let you know.

  • Thanks 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Dario
      Hi everyone!
      As I said few days ago in my presentation I recently got my first scope  (skywatcher 127) and over the last days I tried to test It.
      Due to impossibility (temporary) to bring the scope in a decent location to make observations, I had to test it from home through a window  (and under the sky of London - not the best at all). So i know that quality is of course affected.
      On the other hand, I am sure that the performances are worse than I could expect also under these conditions (maybe you will correct me) and would asks for opinions to improve.
      As a (mainly) planetary scope, I did not have a lot of choice: no Moon, Jupiter and Saturn out of my field of view. I pointed at Mars.
      First sight, I see the very big central obstruction. I played with the knob of the focus to get rid of the big black spot in the centre of my target and here you are the issues that I would like to talk about:
      1) the target became very small (ok) but still was not focus  (very blurry and not a lot of clues to get atleast the shape of the planet well defined - can imagine to find any detail on it )
      2) Also the colours did not convince me as no other colour than a light yellow was visible
      3) Changing the eyepiece  (10 instead of 25) for a magnification of 150x did not improve the situation: probably the image was even worse, more blurry with more irregular shape than before, no ability to focus at all. Differences from before : bigger (but still much smaller than expected) and very little variation in colours (I believe I saw a bit of orange).
      To complete, later, I tried the scope to stars: Orion costellation was visible from my place and tried to all the stars. Although still a bit blurry  (the brightest stars), I had impression of more sharp view, differentiation in colour and better shape  (stars almost like a dot). Moreover, to give you a final idea, Mars (at the best focus I could get) did not appear that much bigger than Betelguese.
      What do you think I can do to get better results? Could be a scope problem or some adjustments needed? Unfortunately I have no comparisons. 
      Thank you, Hope I was not too long 😅
    • By JimFR
      I’ve just acquired the above (birthday prezzie!).
      It’s a nice finder, and a definite boost from the 7x30 bundled with the scope!
      However, I’m struggling to get anywhere near focus with my Pentax K50 on the end of it... anyone know why? There’s no focus mechanism to speak of, other than the objective lens’ mounting thread...
    • By Padraic M
      I spent the full night out last night and got 6 hours of Ha lights on the Bubble and the Horsehead. Reasonably pleased with the results, but even though I followed my usual process and got good focus statistics in APT, I am slightly out of focus with roundy stars and some are even slightly donutty. Samples are attached below.
      Problem:
      - After getting close to spot-on focus, the APT Bahtinov Aid showed a focus distance oscillating from -0.02 to +0.02. Seeing seemed good to the inexpert eye. Not so sure about transparency as there was some thin, wispy cloud throughout the night. So, I started the night's imaging with focus 'Close' rather than 'On' focus.
      - Different subs show different quality stars, ranging from small donuts to circles.
      Background information:
      - HEQ5 Pro Rowan; SW Esprit 80 with field flattener, SW stock manual Crayford focuser; ZWO EFW Mini; Baader 1.25" 3.5nm Ha filter; ZWO ASI1600MM Pro binned 1x1 @ -20c.
      - AA Starwave 50mm guidescope with ZWO ASI290mm Mini guidecam binned 2x2.
      - All subs are 300s, gain 139, offset 10.
      - Polar alignment with Sharpcap to 17 arcsec ("Excellent"); capture with APT; guiding with Phd2. Focus with Bahtinov mask and APT Bahtinov Aid. Stacked in DSS with Darks, Flats and Dark Flats.
      - Mount is well balanced in RA, but is very camera-heavy in Dec.
      - PHD2 guiding was around 2"/px. Imaging pixel scale is 1.9"/px.
      Questions:
      - Do I put the round stars down to seeing, given that the Bahtinov Aid focus distance was bouncing equally above and below zero?
      - Can poor seeing cause the donut stars?
      - Would an electronic auto-focuser do any better in this situation?
      - Would the Seeing Monitor in Sharpcap give useful information? I didn't think to use it last night.
      - Could my guiding performance, and possibly the Dec balance, have affected the image quality in this way?
      - What are my options in future - abandon imaging for the night? Bin all images in software 2x2 or 4x4 to sharpen the stars at the expense of lower resolution?
      - Other suggestions?
      Sample 1: Detail from a single 5-min sub of Bubble nebula at 100% showing round stars, and a blurred bubble.

      Sample 2: Detail from a different sub of the Bubble nebula at 400% showing donuts

       
      Sample 3: Detail from a 5-min sub of the Horsehead nebula at 100%, showing both round and donut stars

       
      Finally, both images stacked, calibrated and stretched, scaled to 4x4 in Gimp. 28x300s Ha on bubble, 22*300s Ha on horsehead.


    • By Emilio
      Hello all,
      I'm new to this forum and astrophotography, and observing for that matter!
      I've been observing for a few weeks now, well, when the clouds allow, obviously! I thought I'd dip my toe in the water as far as imaging goes, but didn't want to go nuts in terms of budget. As luck would have it I managed to get hold of a Canon 1100D on eBay complete with full spectrum mod for £129, which seemed pretty reasonable to me given the cost of the modification on its own. The camera is in great condition and seems to work fine, however I have a couple of queries that I hope you more experienced peeps can help with.
      Firstly I would like to get an OWB filter and wondered if anyone had an opinion on Optolong vs Astronomik? Astronomic are a lot more expensive so if the Optolong does a good job why spend extra?
      Second, and more importantly, I have questions about auto focus. It seems that generally people say that if the IR/UV cut filter is completely removed then the camera will definitely lose the ability to auto focus (although some people say this isn't the case?). I checked with the eBay vendor and he confirmed that the in-built filter has been completely removed and no glass / filter replacement has been put back in place, which if my understanding is correct is what is required to retain auto focus. However, the camera seems to be auto focusing fine as far as I can tell.
      How can this be?
      Thanks.
    • By Steenamaroo
      Hi all,
      I've been dabbling for about a year and am having a lot of fun.
      Nothing too serious and I don't have mega expectations but I'm starting to wonder if my images could be sharper and there's something I'm missing.
       
      I'm attaching a picture which is the best 10% of a 3 minute video with 500d 'bolted' straight to the 200p f5 scope. No filters...no barlows...just camera straight on.
      It's sharpened and saturated after the fact so in every way this is the sharpest I can get it.
      I've always had the same issue whether it's with a single shot, stacks of shots, or stacked video.
      Views through the eyepieces (circle-T 12.5/25) are mega sharp!
       
      I'm happy that collimation is very good and it was a remarkably clear night tonight.
      All in all I'd be pretty happy with this image (maybe over exposed a bit...) if the craters with shadows didn't make me want to rub my eyes.
       
      Thanks in advance for any thoughts or advice!

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.