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Posts posted by SteveP

  1. Now I'm confused!

    Chris - When you refer to 'dark flats', do you mean 'dark subtracted flats' ie you have taken a flat and from it deducted a dark to remove any dark current? This is what I had assumed you had done. If that is the case than deducting (strictly speaking dividing by) a flat and also a dark flat will result in over calibration

    Rob on the other hand uses the phrase 'flat dark' and I don't then disagree with anything he then says about using a flat dark.

    Can youjust clear up this point?


  2. I am still trying to figure out the trailing in the corners of the image (http://stargazerslounge.com/imaging-image-processing-help-techniques/150570-stretched-stars-edge-image.html). I am unsure if it is field rotation because if I stack the full 3 hours worth of subs without alignment the trailing does not get any worse than in the individual subs.

    One simple way to check whether it is field rotation is to take a set of individual subs at different exposure times eg 1 min, 2 mins, 3 mins and see whether the trailing gets progressively worse


  3. Chris

    I think you may have misunderstood something. A dark flat is not the same as a bias frame. A bias frame merely captures noise which is fixed and independent of exposure time. The reason why dark flats are used is to remove the bias component from a flat. In practice, they are not used very often. Also, you may need bias frames only if the darks have to be scaled.

    What software are you using to calibrate the images? THere may be something unusual in the way it sequences the processing

    Having your dewshield on the scope shouldn't impact on the quality of your flats.

    If the star trailing is independent of exposure time then you may need to look elsewhere. Something may well be moving in your imaging train. I'd start be checking all the connections especially any which have a compression fitting


  4. I'm puzzled as to why you are applying both flats and dark flats. If you really are doing that then the flat is being applied twice which is why you appear to have an over calibrated image. My advice would be to re-process the image by calibrating with just flats and darks if the darks are at a similar temp to your lights.

    You also seem to have some field rotation as shown by the 'circular' star trailing towards the corners. Field curvature problems would typically give rise to radial star trailing



  5. Andy

    As others have said, SX's Star2000 uses one chip for both imaging and guiding. That approach is however no longer used. Have a look on the SX site for the appropriate software.

    I also see that you're using Maxim. I think Maxim can use Star2000 with the appropriate drivers. If you search on Star2000 on Maxim's Help, i'm sure you'll find something to set you in the right direction


  6. Alan

    Unfortunately it depends on the mount itself! Some store the PEC information whilst others have to have it replayed every time. I've no idea whether the CGEM does or doesn't. The best source of mount specific info is often the manual.

    Which PEC software have you used? If it's PemPro, have a look on the PemPro support site. Ray Gralak who wrote PemPro is always available and offers excellent advice


  7. Harry

    Contact Brian Brooks at astroparts.co.uk He's made a few adapters for me for assembling CCDs, filter wheels, etc and he has always been reliable. His prices are reasonable given the custom nature of these things


  8. Hi Paul

    I can't help you specifically with PHD but here's what I do using Maxim to both guide my mount and acquire the images

    1. Link all the various bits together (mount, imaging camera, guide camera, focuser etc ) including having the guide camera connected to the mount's ST4 autoguiding port and the various connections made to the laptop

    2 Polar align the mount. I use PemPro and try to get it to within 3-4 arcmins of the pole

    3 Align the mount for accurate GoTo's - I happen to use Maxim's version of plate solving for this in conjunction with TheSky6 using the Sync command. Effectively it's a 3 star alignment but I tend to use 6-8 reference points

    4 GoTo the object I intend to image

    5 Start the autoguiding process within Maxim, ie find a guidestar, and then calibrate the mount. This important stage tells Maxim how to correct the mount as the signals from the guide camera are received. I expect there to be something very similar in PHD

    6 Once the mount has been calibrated, start autoguiding on the guidestar and wait for it to stabilise

    7 Start imaging

    I suspect that one area you'll need to look at in particular are the detailed PHD settings, eg aggresiveness or whatever PHD might call it, which is how you fine tune the software to your particular set-up. There are some examples on SGL of what others have used successfully in PHD. You might want to have a look at them

    I hope that this gives you some ideas about how I do it which you can read across to PHD


  9. Paul

    What you've described is the process for aligning your scope for GoTo purposes. When autoguiding, this is still required in that it helps to find targets that much easier. However in addition, you also need to 'polar align' your mount as well, ie align the mount so that it is parallel with the earth's polar axis. There are several ways to do this including manual drift alignment or software controlled using a CCD or webcam.

    If you have a search on here, you'll find lots of advice on the different approaches for polar alignment. I'm not familiar with PHD so can't comment on whether it incorporates any polar alignment routines itself.



  10. Rob

    I suggest your problem lies with the master flat itself. If you look carefully, the flat contains a galaxy-like artefact at the bottom-middle which accords with a similar artefact on the light. After applying the flat, this artefact disappears in the calibrated frame as you'd expect. However, those weird raindrop type artefacts around the edge of the flat have just been reversed on the calibrated frame which suggests to me that these artefacts aren't a permanebt feature in the optical train.

    Have a look at all of the individual flats and see if there is anything strange on any of them


  11. Welcome to SGL

    I'm a little confused by what you have shown in the photograph. I recognise ADM's Vixen style dovetail but I'm not sure about the other piece. Have you photographed the base of the scope's mounting rings?

    If so, both mounting rings are attached perpendicular to the dovetail. With both rings installed and bolted tightly through the dovetail, you should find that the stability improves. Unfortunately, this design of dovetail doesn't provide much of a platform on which to attach the mounting rings.

    What scope are you mounting and onto which mount?



  12. Ian

    It's good to hear of somebody thinking about the future use for their equipment. If you are serious about wanting to get into astophotography, then investing in the best mount you can afford is the way forward. An EQ6 Pro would be an excellent platform and you have to spend considerably more to improve on its capabilities.

    Whether you need GoTo is an important consideration. Without doubt you will need some way to target your imaging subjects. There are two ways to do this. Firstly, and easiest, via the mount's own GoTo facility. As you've realised, you'll pay extra for this with the EQ6. Secondly, by using EQAscom (sometimes known as EQMod) which is freeware and excellent! It's used widely with HEQ5 and EQ6 mounts. However, it would be best used in conjunction with planetarium software (some of which is freeware) and needs a small adapter and a couple of cables. It might cost you £70-80 for the extra bits. It also needs a laptop!

    So far as a scope is concerned, you'd do well to heed the advice above



  13. Chris

    I expect at some stage you will want to increase the subs' exposure to more than the 15-30 secs you will get from your LX90's mount. As well as the need for an equatorial wedge, you will in all probability want to autoguide the mount. Unfortunately, most LX90 mounts (I'm not sure about the most recent models) are only capable of accepting standard 'ST4' autoguiding commands when used in conjunction with a particular Meade accessory called APM909. The bad news is that Meade haven't exported them to Europe for several years and now no longer manufacture this part. You might be lucky and find a 2nd hand one or there are wiring diagrams on the web for DIY'ers.


  14. Rob

    I did have this problem when using an Astrodon MOAG with a FSQ 106ED. The elongated stars are caused by the prism not being fully parallel in the light cone and is most common with fast scopes, ie a steep light cone, and large chips. It didn't create a major problem with tracking but occasionally Maxim would get its knickers in a bit of a twist. Interestingly, the same MOAG had perfectly round stars on a slower (f7) scope

    Don at Astrodon suggested that I slightly tilt the prism away from the direction of the light by adding slivers (about 8mm x 3mm) of sticky aluminium tape under the leading edge of the spacers which attaches the prism to the MOAG body. Trial and error showed that two pieces of tape were sufficient. Now I have round guide stars again

    Why not also give Terry at SX a ring. He may have come across this problem already. I know he uses a fast scope (f5) himself



  15. Yes, they're dust motes.

    You could try cleaning the sensor itself but that is a very tricky operation. Depending on the design of your camera, there might be a clear 'window' in front of the sensor which is much easier and safer to clean than the sensor itself.

    If the cleaning either can't be done or still doesn't get rid of all of the dust (some dust particles are usually very stubborn) then the conventional way to counteract the dust on the image is to apply flat frames to the image during the calibration stage.


  16. I'm buying a s/h EQ6 but it has no mounting gear to fasten the scope to the mount. In this case, and given that my scope is "only" a SW102 refractor with dovetail fittings, what do I need to buy to mate the two?


    Probably nothing. The dovetail which is included with your refractor should fit the puck of the EQ6 without any additional fittings. It just slides it and retained by two screws


  17. Since you intend to image with it, my personal preference would be to avoid using the stock Meade focuser knob if at all possible and attach a motorised Crayford onto the rear of the OTA. There's more than sufficient back focus to not have to worry about it. It's probably a more expensive option but well worth the extra



  18. Peter

    In Maxim, open the Obs Control tab - looks like an observatory

    Go to Telescope

    Click on Options>

    Select Choose

    The Ascom telescope chooser should appear

    Select your scope from the drop down (I'm guessing at something like LX200 with Autostar)

    Click on Properties and make sure that the Com port selected is the one allocated by your laptop when you plug in the scope's serial adapter

    Click OK and go back to Maxim's Obs Control screen

    Click on Connect in Telescope section

    ... and Maxim and your scope should be connected together

    All your settings should be remembered for the next time. Then, all you need do is go the Obs Control tab and press Connect under Telescope

    I suggest you do this during daylight so that you're familiar with the process for when a clear night appears!



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