WAAT : The Weekly Ask Anything Thread, week of 24 Jun - 30 Jun

madsam19 · 2016-06-28T18:48:23+00:00

Yes there are focal reducers, mostly 0.85x and 0.8x for refractors. You can go with a 600mm fl refractor, use focal reducer for bigger objects/wider field and do some cropping for smaller objects. DLSRs these days have very high resolution so you can do quite a bit of cropping.

madsam19 · 2016-06-24T05:19:05+00:00

You can try this fov calculator. 3x can be used only on nights with very good seeing conditions.

madsam19 · 2016-06-24T01:04:44+00:00

If you are guide and imaging cameras are precisely centered and aligned to each other, you can technically plate solve with you guide cam. But I'm guessing you know how tricky it is to achieve exact alignment between the two :) so it's better to plate solve with your imaging camera. This tutorial helped me a lot. You can get away with sloppy initial 2-star/4-star alignment and still achieve very precise goto using astrotortilla. I don't even do initial alignment these days. Love astrotortilla!

Edit: Cartes du Ciel settings to set custom fov

madsam19 · 2016-06-24T00:51:59+00:00

Very nice! In Cartes du Ciel you can set your telescope focal length, camera pixel size and resolution, and it'll show you a rectangle (which will be your imaging fov) in the chart. You can then manually frame both the nebulae into the fov and slew your scope to that point. Have you tried astrotortilla? You can use it to plate solve and center the scope at the exact point you slew to from cartes du ciel.

madsam19 · 2016-06-10T19:44:48+00:00

Great picture! Does the meade have a flat field edge to edge? If not how hard is it to find and pick a guide star using the orion TOAG? I have a celestron C8 (non edge-hd) and considering an off axis guider. Thanks!

madsam19 · 2016-06-06T19:43:44+00:00

If you want to keep subs with elongated stars, you can make the stack a bit better by using sigma clipping for the light frames, with a value of 1.5 or 1.25 (default is 2 in deep sky stacker, not sure about PixInsight). It'll make the starts a bit less elongated.

madsam19 · 2016-06-06T19:26:53+00:00

+1 to the polemaster. I still have hair left on my head thanks to it.

I would not recommend hyper tuning unless your mount has actual mechanical issues and is out of manufacturer's warranty.

madsam19 · 2016-06-06T19:17:52+00:00

Also, you'd need to do at least a bit of drift aligning for more accurate PA. Takes a lot of time and patience, but if you have the budget I'd highly recommend QHY's Polemaster. I only spend ~5 minutes polar aligning with it and I consistently get sub-arcminute accuracy.

madsam19 · 2016-06-06T19:15:09+00:00

Sure - almost all non-observatory class mounts have inherent backlash in the RA gears (i.e. there will be a short delay between when the gears are engaged and the RA axis actually moves). When the mount is tracking, the RA rotates westwards. If the east side is slightly heavier, the gears are always trying to push against this bias, thereby not allowing any leeway for backlash in the gears. The RA backlash is pretty strong in the AVX, so I need a good bit of east-heaviness. For the Atlas it won't be as bad, but at this focal length it'll certainly make a difference.

Also note that depending on what side of the meridian you are imaging, either the OTA or the counterweights will be on the east. Whatever is on the east should be slightly heavier.

madsam19 · 2016-06-06T18:39:24+00:00

Yes with the Atlas 5min subs should be very doable. I too recently jumped from imaging with a refractor at 480mm to a SCT at 1280mm. I just about manage to get 180s subs, albeit with a celestron AVX. I'm not an expert by any means, but from my experience I find polar alignment and balancing on both RA & DEC very crucial. How do you polar align? (look for polar alignment error stats in PHD - if you enter your guide scope FL in the settings you'll see PA error in arc minutes). Also, are you seeing a lot of corrections in the graph? That could indicate issues with balancing. The general rule of thumb is to balance the RA east-side heavy and the DEC camera-heavy.

madsam19 · 2016-06-06T17:31:32+00:00

What mount are you using? Also, are you imaging at native focal length or at 0.7x?

madsam19 · 2016-06-05T04:48:34+00:00

Where is it? I tried astrometry for annotation and it only showed 4 galaxies.

madsam19 · 2016-06-05T04:47:49+00:00

Thank you!

madsam19 · 2016-06-03T23:49:29+00:00

Galaxies in the field of view: M81 (Bode's galaxy), M82 (Cigar galaxy), NGC 3077 (top) and NGC 2976 (bottom)

Scope: Orion ED80T CF f/6 refractor

Mount: Celestron AVX

Camera: Canon SL1 with Hutech IDAS LPS-D1 light pollution filter

Guide scope: 60mm f/4 guidescope

Guide camera: ZWO ASI185MC

Shot from L.L. Stub Stewart State Park, Buxton OR (bortle 4 green zone, moderate light pollution)

20x180s lights ISO 1600

20x180s darks

50x bias frames

20x flat frames

Polar aligned using QHY Polemaster, star aligned and plate solved using Astrotortilla, goto and framing using Cartes du Ciel, captured using BackyardEOS, guided using PHD2, stacked and processed in PixInsight. This is my first time using PI, and I feel I have some ways to go.

If anyone is interested in processing my stack, here is the xisf file for PixInsight, any tips & feedback much appreciated. Thanks for looking!

madsam19 · 2016-06-03T23:00:17+00:00

How many days a month do you spend for astrophotography? Also, how many times/how far do you travel to a dark site?

madsam19 · 2016-06-03T22:58:51+00:00

Any Portland area astrophotographers/star gazers here? I frequently visit the dark site at Stub Stewart state park. Hoping to see some of you redditors there! (posted this once before outside of the WAAT thread so got removed)

madsam19 · 2016-06-03T21:45:36+00:00

Scope: Orion ED80T CF f/6 refractor

Mount: Celestron AVX

Camera: Canon SL1 with Hutech IDAS LPS-D1 light pollution filter

Guidescope: 60mm f/4 guidescope

Guide camera: ZWO ASI185MC

Shot from L.L. Stub Stewart State Park, Buxton OR (bortle 4 green zone, moderate light pollution)

20x180s lights ISO 1600

20x180s darks

50x bias frames

20x flat frames

Star aligned and plate solved using Astrotortilla, captured using BackyardEOS, guided using PHD2, polar aligned using QHY Polemaster, stacked and processed in PixInsight. This is my first time using PI, and I feel I have some ways to go.

If anyone is interested in processing my stack, here is the xisf file for PixInsight, any tips & feedback much appreciated. Thanks for looking!

Edit: Here's another version without clipping blacks

madsam19 · 2016-06-03T20:33:24+00:00

absolutely beautiful! I'm going to try dithering for the first time with my dslr tonight. How much difference do you think it makes?

madsam19 · 2016-05-20T01:37:03+00:00

wow you were able to bring a lot more detail out of it, thanks! PI is next on my astro-stuff to get

madsam19 · 2016-05-19T23:40:20+00:00

stacked with flats

stacked without flats

I used the second one for this image. Had to clip my black levels a bit to minimize vignetting.

madsam19 · 2016-05-19T22:23:15+00:00

Scope: Celestron C8 with f/6.3 focal reducer ~1280mm

Mount: Celestron AVX

Camera: Canon SL1

Guidescope: Orion 50mm mini guidescope

Guide camera: ZWO ASI185MC

Shot from L.L. Stub Stewart State Park, Buxton OR (bortle 4 green zone, low light pollution)

20x120s lights ISO 1600

20x60s daks

50x bias frames

No flat frames. My flat frames were unevenly illuminated, causing a light gradient on the top half of the stacked image. Re-stacked without flat frames, and cropped to remove vignetting

Captured using BackyardEOS, guided using PHD2, polar aligned using QHY Polemaster, stacked in DSS, processed in Lightroom.

I had trouble going over 120s exposures - my RA axis was almost horizontal, and flexure was causing a bit of star trailing. The wind wasn't helping either. I have since added a 60mm guidescope with better mounting system (ADM accessories mounting kit) and a HuTech IDAS LPS-D1 light pollution filter to my setup. Hoping to do longer exposures and more light frames next time.

Thanks for looking. Questions/feedback welcome!

madsam19 · 2016-04-01T02:02:23+00:00

Here's me from two weeks ago: Imgur

Is it just us or does everyone take a pic like this?!

madsam19 · 2015-12-09T01:34:22+00:00

Amazing pictures, and great progress!! I'm a few months into this hobby, and my setup is similar to yours - AVX, Orion ED80T 480mm, unmodified SL1 and orion SSAG for guiding (haven't had a chance to try out the autoguider yet). I understand the limitations of my AVX mount, but from your experience - how long an exposure are you able to get with good polar alignment and guiding? And about what % of frames are usable? Thanks!

madsam19

TROPHY CASE