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Owmuchonomy

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Posts posted by Owmuchonomy

  1. Hi Adele, welcome to SGL.  Regarding lightweight for a backpack, don't discount a good pair of binoculars.  If you are happy to use resources such as the book Turn Left at Orion to find targets then it may be a good starting point.  Enjoy.

  2. All good advice above.  I'm not as clever as those guys so I use a simple formula whereby the ideal focal length is 5x your chip pixel size.  So if your pixel size is 5 microns you need to aim for f/25; for 3 microns, f/15.  That said there are other factors I also find critical, predominantly defeating the seeing conditions.  That is all about collecting frames during the best seeing so I aim for at least 80fps and use an IR pass filter where possible.  As @vlaiv says aim for very fast shutter speeds and a high gain setting.  I use flat frames but never bother with dark frames for lunar with my cameras (ASI174MM and ASI290MM).  Lunar imaging is very rewarding so have a go and enjoy the results.  Below is an example using the 'widescreen' format 290 chip.

    32610865803_7d0cf51831_o.thumb.jpg.ba0661886f457cc3e48d1de35e796d12.jpg

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  3. We use Lunt and PST specifically designed Ha solar scopes.  We do not attempt WL observing.  We also give a preamble on never looking at the Sun without properly designed equipment supervised by experienced solar observers.  Never leave the equipment unattended.  We had a great turnout for the Mercury transit.

  4. If you purchase a solar filter (https://www.firstlightoptics.com/solar-filters/astrozap-baader-solar-filter.html) for your 150 PDS you will be able to image in white light only.  You could make your own with Baader film too. The only features you will pick up are sunspots or in periods of great seeing you may resolve some surface granulation.  You can use your Nikon at prime focus but it's best to take high frame rate video and stack the results to get a final image.  Best to use your ZWO ASI 120MM but check with the FOV calculator on the FLO site to see how much of the solar disk you can accommodate with that chip in your system.  Remember to remove any finder scopes when observing the Sun!

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  5. In order to satisfy your desire for long exposure astrophotography you have to remove all the artefacts produced by the Earth’s rotation, for example, star trails. To do that you need a device that is perfectly aligned to the Earth’s axis and rotates at the same pace as the Earth. That device is an EQ mount. The mounts are often fitted with polarscopes perfectly aligned to their axis. The orientation of other attachments such as cameras and telescopes is largely irrelevant. ‘Attaching’ a polarscope won’t give polar alignment. Your best bet is to invest in a decent EQ mount or try one of the electronic methods described above and see how it goes. If you have fixed focal length TP lenses eg 300mm try those first.

  6. I hope you can solve the problem.  Try and separate the two main functions of GoTo accuracy and PA accuracy.  They are not necessarily completely interdependent.  For observing it is a high priority for accurate GoTo but PA accuracy is less critical.  For imaging it is very important to achieve very accurate PA but your mount must also be in tip top condition, without backlash in the axes for example.  For accurate GoTo I would suggest you use the 3 star alignment as in your original set up.  This process adjusts for cone error in your setup.  Make sure when aligning stars in your eyepiece that you finish the centreing with an UP and RIGHT touch on the handset.  I would suggest not using a camera for the GoTo setup.  Mounted cameras do not necessarily mount in a concentric fashion.  Use a high power reticule eyepiece if you have one.

  7. The three star routine is best avoided for Synscan Polar Alignment.  Its primary function is to the correct cone error of your optical tube.  To perform an accurate polar alignment of your mount, first ensure the OTA is in the home position and the EQ axis roughly pointing to Polaris.  Ignore the polarscope.  Next perform a two star alignment using two stars on the same side of the meridian that you will be imaging your target. Then run the polar alignment routine on the Synscan menu.  After 2 or 3 iterations of the Synscan routine using a high power eyepiece the polar alignment should be very accurate.  At no point do you need your polarscope.

  8. The Sun's disk currently has two active regions.  One of them has a visible spot on the receding limb at about 4 o'clock.  That should be easily visible with your set up.  Use your 40mm EP and get the Sun's limb in view then check focus carefully.  Other than spots you are not likely to pick out any detail in white light unless the seeing is spectacularly good when you may see some faint granulation.

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  9. 51 minutes ago, Louis D said:

    The primary is about an f/2 concave, thus the very short tube.  The secondary is about an f/5 convex, thus the magnification to a combined f/10 system focal ratio.  Both mirrors are spherical.

    To correct spherical aberration, the corrector plate is aspherical.  The resultant system also has low astigmatism.

    An SCT has uncorrected field curvature and coma in its standard commercial form.  That's why there are various correctors for them for photography that are placed near the rear port.

    Excellent description and succinct.

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  10. A very good experience with both my AzGti and AZ EQ 6 wifi operation.  Both mounts are also compatible with a handset.  I use iPhone and the Synscan PRO App which is clever enough to know which mount I'm using and if it's Az or EQ setup.  Make sure you get the pro version of the App not the standard version.  It's very easy to use and I even let the visitors to the obsy use it (particularly the younger ones who can work it instantly!).  There's nothing to be concerned about; if I can work it anybody can.  The only hidden items I know about are for solar tracking (quite rightly).  Once you know where they are it's straightforward.

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  11. During our outreach sessions at the obsy, by far the easiest option for us is a small refractor on an iPhone controlled Az-Gti mount.  We just pick the whole thing up and walk outside with families and set it up in minutes.  It requires a 12V supply, either mains or battery.  I use a cordless drill battery (USB output) through a 5V to 12V converter lead.  It will last many evenings between charges.  I personally wouldn't use the MAK we also have because its a bit like looking down a tunnel (narrow field) and focussing a MAK is not for little hands.  Your budget is more than enough to cover this even with an upgraded tripod.  This package is perfect for the children (supervised). https://www.firstlightoptics.com/startravel/sky-watcher-startravel-102-az-gte.html

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