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Useful tip for G11 Digital Drive owners: https://nova.astrometry.net/

Ian Taylor All Messages By This Member #69906 Hello - I do astrophotography on a Digital Drive G11 - one problem I have had in the past is that if I use the finderscope of my telescope to find a bright star, then centre it in my main telescope, set the setting circles to the star's coordinates, I then have to refocus the main and guider camera, before moving to the position of the object I want to photograph.? Maybe it is obvious to others but I have now started to use??- you simply point your main telescope in roughly the right direction of the DSO, and take a photograph. Then you upload the photo to??which after a minute or so tells you the exact RA and DEC coordinates of the middle of the photo. You can then set the setting circles to these values and can then quickly move to the DSO coordinates.? This does depend on you having internet access on your computer when you are observing, but is a neat trick for those G11 owners that don't have Goto.? My main telescope has a focal length of around 700 mm (or 500 mm with a focal reducer) and when coupled with a ZWO ASI 071 camera, the field of view is about 2 degrees by 1 degree, so the above method should enable you to get the DSO in the field of view of the camera, and you can then use the hand controller to centre it.?
Mark Christensen All Messages By This Member #69908 Robert, Nice tip. I'll bookmark the site for use at home - I can't use it in the field but it is nice to have the option at home. The way I have gotten around this problem is to use a flip mirror on my finder/guider and then at the start of the evening (I have to set up and tear down every night) verify that the imaging scope and the guider are co-boresighted so the finder/guider is always pointed at the same spot in the sky as the imaging scope (usually 1100mm with an APS-C sized CCD chip so my FOV is roughly the same as yours). I slip-focus the eyepiece (if used) in the imaging scope when I do this so I don't have to touch the focus knob on the imaging scope. That way I don't have to radically re-focus the imaging scope after installing the camera for the evening - I do a one-time focus tweak of the camera each evening or between shots, if required. Such is the price of working from the trunk of car. The guider is set up so the guide camera and the eyepiece of the flip mirror on the finder/guider have a common (para-) focus. Doing this requires enough in-focus of the guide scope but the 80X500 short tubes commonly used have a lot of that. When imaging at shorter focal lengths (under 700mm or so) I just use a modified 8X50 finder. There I had to hacksaw off about an inch from the tube to get the required in-focus. See: I also built a slightly bigger (and marginally more expensive) version from one objective cone of a 15X70mm Celestron Skymaster bino and a Vixen flip mirror, using the other objective cone to make a wide-field scope.? I bought the binos decades ago (when the price was $58) and didn't use them much. Re-used both eyepieces as well. Regards, Mark Christensen
Paul Homer All Messages By This Member #69914 开云体育 Robert, There are two things I don’t understand about what you say. 1) Do you align the main and finder scope before doing this? Is so, then once an object is centred in the finder it should be centred in the main scope as well. 2) Why do you have to refocus after adjusting the setting circles? Paul toggle quoted message Show quoted text On 27 Jan 2021, at 10:39:09 pm, robert.ian.taylor@... wrote: Hello - I do astrophotography on a Digital Drive G11 - one problem I have had in the past is that if I use the finderscope of my telescope to find a bright star, then centre it in my main telescope, set the setting circles to the star's coordinates, I then have to refocus the main and guider camera, before moving to the position of the object I want to photograph.? Maybe it is obvious to others but I have now started to use??- you simply point your main telescope in roughly the right direction of the DSO, and take a photograph. Then you upload the photo to??which after a minute or so tells you the exact RA and DEC coordinates of the middle of the photo. You can then set the setting circles to these values and can then quickly move to the DSO coordinates.? This does depend on you having internet access on your computer when you are observing, but is a neat trick for those G11 owners that don't have Goto.? My main telescope has a focal length of around 700 mm (or 500 mm with a focal reducer) and when coupled with a ZWO ASI 071 camera, the field of view is about 2 degrees by 1 degree, so the above method should enable you to get the DSO in the field of view of the camera, and you can then use the hand controller to centre it.?
Ian Taylor All Messages By This Member #69916 Hello Paul - yes I check that the main and finder scope are aligned and centred, but I usually do this visually, and the issue is the focus point for the eyepiece for the finder and main scope is different from that of the cameras, so once I have found a bright star whose position I know, you then have to refocus the cameras.? What I am suggesting is that you can bypass the visual step by just pointing the main telescope, with camera focussed, on a random bit of sky somewhere in the region of the DSO, upload the photo to the??website, and after a couple of minutes that will tell you the exact RA and DEC position of the centre of the photo, which you then set on your setting circles, and then you can move to the coordinates of the DSO for the photo session. Incidentally, I have recently got a new ASI 071 MC Pro Cooled camera, and am seriously considering ditching autoguiding altogether, for simply taking short exposures of 10-20 seconds, and stacking hundreds of images (with the gain set to 200 and offset to 60). If this works it will mean I don't need to autoguide at all. For the image scale I have and the periodic error of my mount, 10 or 20 seconds should be OK for tracking.?
Paul Homer All Messages By This Member #69945 开云体育 Robert, I get you now, I assumed you just used the finder scope by eye not the main scope. Seems like a good approach if you don’t have go to though. Paul toggle quoted message Show quoted text On 28 Jan 2021, at 9:39:41 pm, robert.ian.taylor@... wrote: Hello Paul - yes I check that the main and finder scope are aligned and centred, but I usually do this visually, and the issue is the focus point for the eyepiece for the finder and main scope is different from that of the cameras, so once I have found a bright star whose position I know, you then have to refocus the cameras.? What I am suggesting is that you can bypass the visual step by just pointing the main telescope, with camera focussed, on a random bit of sky somewhere in the region of the DSO, upload the photo to the??website, and after a couple of minutes that will tell you the exact RA and DEC position of the centre of the photo, which you then set on your setting circles, and then you can move to the coordinates of the DSO for the photo session. Incidentally, I have recently got a new ASI 071 MC Pro Cooled camera, and am seriously considering ditching autoguiding altogether, for simply taking short exposures of 10-20 seconds, and stacking hundreds of images (with the gain set to 200 and offset to 60). If this works it will mean I don't need to autoguide at all. For the image scale I have and the periodic error of my mount, 10 or 20 seconds should be OK for tracking.?

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