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C8 Schmidt-Newtonian Frakenscope

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#76 Michael Miles

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Posted 07 August 2014 - 03:49 AM

OK, first bad news...

 

I thought about what I was seeing through the eyepiece, and realized that the focal plane of the system was barely outside the Hyperstar.  So, I took some measurements and saw that the hyperstar was located too far away from the optical axis of the main mirror.  Part of the problem is the thickness of the oak board I have it temporarily mounted on.  I did get some 1/4 inch aluminum plate which I can use, but that will only make about 1/2-3/4 inches difference.  I remounted the location of the hyperstar closer to the main mirror, and put the secondary on the centerline (gave me another 1/2 inch), but now the main mirror baffle sticks into the optical train from the secondary.  I don't think there's much I'll be able to do about that at this point.  The changes I made got me close to the 39.8mm backfocus specified on the Starizona web page.

 

So, I may try some imaging with the current setup, but don't hold out much hope for this configuration.  I have figured out a simplified mount for the hyperstar in the usual front-tube position, so I think I may try that next.  I just need to figure out how to make the part safely  (one cut is kind of tricky).  I also need to figure out how to mount the Canon EOS-M on the hyperstar, but that's mostly a case of measuring the thread pitch on the hyperstar (not a t-thread) and making a custom adapter of the correct length to get that 39.8mm distance to the focal plane.

 

Gonna go toss a coin about the next experiment,

 

Michael



#77 Michael Miles

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Posted 08 August 2014 - 02:53 PM

Hi folks:

 

I took the scope out last night and checked it out with the new hyperstar position.  When I examined the moon through the eyepiece, the image was MUCH better than it was previously.  The moon was sharper over the whole field, and the color abberation I'd seen previously was gone.  I tried taking some pictures with the EOS-M, but the setup was too kludgy to get good results.  I had attached the camera using an Orion afocal camera adapter (which actually worked fairly well).  However, I did not want to haul the whole shebang outdoors, and just cradled the scope in my lap.  Needless to say, the juggling act of holding the scope while trying to use the focus knob, navigate the unfamiliar EOS-M interface and then take the picture was too much.  I did get some pictures, but the motion blur and difficulty focusing led to much poorer results than I saw through the eyepiece.  The quality of the image through the eyepiece seemed extremely good - in fact better than I remeber seeing through the scope in normal SCT configuration.  This may be partly due to the flatter field since my old eyes and presbyopia make adjusting eye focus over the normal C8 field curvature impossible.

 

I'm working on the design of the adapter to connect the EOS-M to the hyperstar.  My plan is to machine an aluminum addon to a standard t-mount adapter.  There are 2 types of t-mount adapters for the EOS-M (that I could find).  The first of these is a long unit that compensates for the missing mirror depth:

 

http://www.amazon.co...for Canon EOS-M

 

The second type is a standard short unit:

 

http://www.amazon.co...2190_TE_3p_dp_1

 

I'm hoping the short unit is real and not just a photo error on amazon.  It will be much easier to modify by just adding a single aluminum piece between the t-mount and the hyperstar.  I'd remove the t-mount thread ring and install my own piece instead.  I'm nervous about machining the threads that attach to the hyperstar since I've never machined threads before.  I've been reading up on it, and it doesn't look too hard, but I know other machining students always seemed to ruin a rod or two practicing threading. 

 

Fingers crossed,

 

Michael



#78 Michael Miles

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Posted 10 August 2014 - 01:56 AM

OK, so the coin flip ended up on modifying the camera adapter I have.  I'm still waiting on the better one, but I've kludged a workable one together.  I machined a spacer from an old eyepiece holder I'd made.  Add the magic of gaffers tape, and voila - hyperstar/camera adapter!  The spacer is gaffer taped to the hyperstar with several layers, and then fitted into the hole in the bottom of the adapter and the set screws were tightened into the gaffers tape.  Not as good as threaded, but a usable kludge for testing...

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Edited by Michael Miles, 10 August 2014 - 04:16 AM.


#79 Michael Miles

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Posted 10 August 2014 - 04:13 AM

FYI, here's where I found the info to make the measurements for the spacer:

 

http://en.wikipedia....EF-M_lens_mount

 

and for the t-mount I modified:

 

http://en.wikipedia...._focal_distance

 

and the hyperstar focal length:

 

http://starizona.com...star/specs.aspx


Edited by Michael Miles, 10 August 2014 - 04:17 AM.


#80 Michael Miles

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Posted 11 August 2014 - 03:30 AM

An extra note:

 

Since the spacer I made was based on an old 1.25 inch eyepiece holder, I can actually use eyepieces for the collimation.  I tried several combinations with my Hubble artificial star today, but I'm not quite sure how to proceed.  I've been looking at this resource for ideas:

 

http://www.weasner.c...t_Newtonian.pdf

 

Anybody have experience with using these or other techniques for collimating a Schmidt-Newtonian?

 

Thanks,

 

Michael



#81 Michael Miles

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Posted 17 August 2014 - 01:09 AM

Hi folks:

 

It will take a a fair amount of work to get the Hyperstar closer to the diagonal, so I've decided to move on with the adapter for the front of the scope.  This will mount the Hyperstar in the normal location, and the Canon EOS-M will be in front of the corrector plate.  I've attached a picture of the machining of the adapter.  It will not have the threads of the Fastar mount, but if this setup works, I'll make one of those later.  In this photo, I'm drilling the 1/2 inch hole for the boring bar, so I can start boring out the adapter for the front of the Hyperstar.

 

I'm hoping to get the adapter finished in the next couple of days,

 

Michael

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#82 Michael Miles

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Posted 18 August 2014 - 01:36 PM

I read an article in Astronomy Technology Today about the Hyperstar, and it mentioned the extreme sensitivity to focusing.  This is consistent with the experience I had with trying to take photographs with the SN setup.  The feathertouch is too pricey, so I've ordered a GSO fine focus attachment that I'll modify for the C8:

 

http://agenaastro.co...pgrade-kit.html

 

I'm also about 1/2 way done with boring the hole in the Hyperstar adapter.  I'm planning on using the normal configuration to get collimation and focusing issues worked out, and then I'll look at doing the SN configuration again to see if it works better.

 

More soon,

 

Michael



#83 Michael Miles

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Posted 18 August 2014 - 04:18 PM

I noticed a shutter vibration when I was using the EOS-M, and I did some digging to see how the shutter worked on the camera.  It uses something called Electronic First Shutter Curtain:

 

http://www.robertoto...hutter-curtain/

 

The good news is that this actually has the least shutter vibration of a mechanical shutter - yay for astrophotography!

 

Looks like I need to turn off the mirror lockup off on my T1i:

 

http://www.krebsmicro.com/Canon_EFSC/

 

Better results with EFSC,

 

Michael


Edited by Michael Miles, 18 August 2014 - 04:24 PM.


#84 Michael Miles

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Posted 19 August 2014 - 07:03 PM

I've finished boring the Hyperstar adapter, and have attached a couple of pictures.  I have the Hyperstar in the wrong end of the adapter to test the fit.  The end of the adapter which is in the lathe chuck will be outside the corrector plate.  I'm seriously thinking about threading the adapter.  I can always cut the threads off if I mess them up.  I've never cut threads before, so I'm a little nervous.  Youtube to the rescue!  I think I can handle this machining task, and it will make the part much better, so it's worth a try.  A little more delay, but worthwhile.

 

Michael

 

 

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#85 Michael Miles

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Posted 21 August 2014 - 11:59 PM

Hi folks:

 

I finished the adapter.  This is the first time I've cut threads on my lathe - and it worked!  YaaaaaY!

 

OK, enough of that...

 

The adapter uses 20 threads per inch (I'd measured the Hyperstar with a thread gauge), and I've posted the O.D. of the threads earlier in this thread (are puns allowed on CN?).  There is a shoulder on the outside of the corrector, and I guessed that it was the same as the similar shoulder on the secondary holder, or 0.157 inches.  If anyone has a Fastar, please verify or correct this number, as I suspect it's critical.  There is a card stock spacer in front of the corrector, and I've got a rubber washer behind the corrector.  I've currently got the adapter attached with a hose clamp, but I will switch to a split clamp if everything works out.

 

I finally figured out how to use the remote on the EOS-M, so I can fire the shutter remotely.  The Magic Lantern software also allows interval timing of multiple exposures like my external interval timer for my T1i.  I also got my GSO slo-mo part (see previous post), and it's in one of the frames so you can see how big it is.  I think it will take 2 couplers to  attach it to the current SCT focuser.  I'll probably start a new thread for this mod since other SCT owners may be interested in this too.

 

Naturally, it's cloudy out tonight when I want to do a first light on the new configuration.

 

Oh, well,

 

Michael

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#86 Michael Miles

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Posted 22 August 2014 - 03:58 PM

I tried first light last night, but focusing was too difficult, so I took it out in the daylight today.  The result was much better than with the SN setup.  I suspect the collimation was off with the SN.  The collimation was rough today, but I checked it with a laser, and it was not bad (by chance).  I'll adjust it tonight, and hopefully get some sort of test shots (depending on clouds).  I'll also post the outdoor photo, so you can see how it looks (and maybe a ratty old SN test photo).  



#87 Michael Miles

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Posted 23 August 2014 - 04:02 AM

OK, here's some photos.  The moon was taken with the SN config.  I suspect collimation was the issue.  The tree picture was taken with the normal Hyperstar configuration (with rough collimation), and jpeg compression has introduced some problems with dynamic range and edge artifacts. The original is much better.  The depth of field is apparent even though the trees were about 75-100 yards away.  The amazing thing about the tree photo is that the camera had to be set to ISO 200, and the shutter to 1/4000 of a second to get the ballpark exposures.  Bodes well for astrophotos!   Naturally, it was cloudy skies at night...

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#88 coinboy1

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Posted 23 August 2014 - 07:39 PM

Love the experimenting that goes with this post. Good luck!!



#89 Michael Miles

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Posted 23 August 2014 - 09:39 PM

This is fru

 

Love the experimenting that goes with this post. Good luck!!

 

     Thanks, the experimenting is what is fun for me too.  I figured out a way to get a slightly better collimation using a de-lensed barlow in the Hyperstar adapter (remember that it used to be a 1.25 inch eyepiece holder before I machined it for the adapter).  The barlow has an eyepiece plug which is translucent with a rib in the middle.  I have a laser collimator in a Zhumell focuser at the back of the C8.  I center the laser line in the translucent plug and then rotate it 90,180, and 270 degrees to verify.  The Hyperstar collimation screws are completely retracted.  I'm thinking about getting a Hotech retroreflector:

 

http://www.hotechusa...ror-p/rm125.htm

 

to give better results.  I know this is only aligning the mechanical components, and that further collimation would have to be done on a star (artificial or otherwise).  Naturally that means that its cloudy tonight...

 

Michael

 

 

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#90 Michael Miles

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Posted 24 August 2014 - 02:26 PM

OK, the clouds cleared in patches enough last night to take the scope out and take some images.  I had to learn some more about how to use the Live View on the camera to focus, and finally realized that I had to turn the LCD brightness all the way up to be able to see stars.  I took several 8-30 second exposures at ISO 3200 to test things on a non-driven mount.  There are still some weird artifacts, so it seems the collimation is still off.  I'm going to try collimating today indoors with my artificial star and see how that works.  It's supposed to be clear tonight.  I'll take my iOptron ZEQ25 out tonight and do driven but unguided shots to see how things work.  

 

Letcha know,  Michael

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#91 Michael Miles

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Posted 25 August 2014 - 07:45 PM

Hi folks:

 

Ok, out last night under the cool clear(ish) skies with my iOptron ZEQ25 this time.  The mount started giving me trouble and not tracking (I've got a CN thread on this, and thought it was fixed...), so I only got one good pic before disaster.   So, I didn't have a chance to tweak the collimation.  I still think this is the problem (see the donuts in lower left) - anybody know differently?  I may make it out tonight for another round.

 

I also got a gizmo which I think will be the best way to create an adapter for the Hyperstar:

 

http://www.amazon.co...0?ie=UTF8&psc=1

 

It has a 52mm thread, and there's a 58mm one available also:

 

http://www.amazon.co...=I2DNFOKG4VRPZC

 

These are lens reversing macro rings, and they screw into filter threads at the front of the lens.  Since the bayonnet is difficult to machine, just buy one of these, shrink fit a filter body in an aluminum piece, and voila - a custom mount for the camera.  The other end of the aluminum piece will be machined for the Hyperstar threads.  Too bad these aren't normal camera filter size, otherwise the same trick could be used for the Hyperstar end of the adapter.  I'm not in a big rush since I've got the jury-rigged adapter, but this is definitely the way I'll go for a permanent adapter.

 

One of these could be used instead of a 52mm filter:

 

http://www.amazon.co...=A3JK7NEF4ES3E9

 

Michael

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#92 Michael Miles

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Posted 26 August 2014 - 12:28 AM

I went out again tonight, and the astronomy gods were with me.  My mount was tracking fairly well, so I don't know what happend last night.  I did fiddle with the Hyperstar collimation screws, but I wasn't able to get a good feel of how to methodically approach the adjustments.  I'll fiddle in the daylight so I can see how the mechanism works and try it again at night.  I don't like 3-point collimation screws, I much prefer 4-point (x-y axis type) ever since I worked on a survey crew - they're much more predictable.

 

On a lighter note, I did get a couple of special exposures that I wasn't expecting.

 

The first of these is the Elm Nebula, and the second one is the iOptron Borealis.  The iOptron Borealis is really special because it requires an open tube telescope to see the effect that atmospheric scientists call "LED fluorescence."

 

Michael

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#93 coinboy1

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Posted 26 August 2014 - 02:21 PM

Love the elm nebula and ioptron borealis! Very rare shots indeed and good job trying!



#94 Michael Miles

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Posted 28 August 2014 - 05:12 PM

Hi folks:

 

I took the Frankenscope out last night with the reversed corrector and got similar results.  The next step will be to remount the optics in the original (oranganal) tube.  That should take care of alignment of the corrector and the main mirror.  However, I suspect the problem is actually my kludgy camera mount (see photos above).  The sensor could easily be misaligned with the optical axis of the Hyperstar.  I've ordered the new parts to make the new adapter which should have much better orthogonality and precision.

 

On the positive side, I did manage to photograph M27 for the first time!  The 8 second exposures make bouncing between targets very quick and easy.

 

Fingers still crossed,

 

Michael



#95 Michael Miles

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Posted 31 August 2014 - 02:43 AM

I figured out a way to get a quicker polar alignment by using my Jasper laser.  I've been having trouble finding Polaris by eyeballing the mount in the dark while bent over upside down.  The solution - I put my Jasper pointing laser in the polar scope hole (rests in the bottom nicely) and get a rough alignment with it first.  It easily places Polaris within 1/2 the polar scope field width, and then I just tweak normally from there.  Saves a real pain in the neck ;) .

 

Michael

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#96 Michael Miles

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Posted 02 September 2014 - 07:05 PM

OK, I did some processing on the M27 photos.  These are 13 of 8 second exposures at ISO3200!  There is vignetting, and maybe I'll post a raw stacked image so you can see that.  The field tilt is apparent here with the off focus stars in the corners, but it does show the huge field of view.  I'm waiting for the moon to get above the trees so I can show a shot with the new setup (verses the SN with bad camera mount).  I need to design the camera adapter and order the aluminum.  I don't have a cutoff saw, so I have to order to length, but onlinemetals.com is good for that.

 

Michael

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Edited by Michael Miles, 02 September 2014 - 10:55 PM.


#97 Michael Miles

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Posted 07 September 2014 - 06:24 PM

I've reassembled my tube with the Hyperstar attached.  I took it out to photograph the moon last night, but had to wait for hazy shots in gaps in the clouds.  I aligned the drift of the moon to travel diagonally across the frame.  There seemed to be a focus shift between the edges and the center of the frame.  This wasn't due to mirror flop since the mount was still.  I also shot some stars, and I still have the c-clip stars in the bottom left corner.  At this point, I'm thinking the issue us the camera mount.  I'll rotate it 90 degrees relative to the Hyperstar optics and see if this shifts the problem by 90 degrees.  If it doesn't, I'll try rotating the whole Hyperstar 90 degrees to see if the telescope optics alignment is causing the problem.  However, we've got a couple of rain days, so it's hurry up and wait until then.  I'm actually liking this camera the more I use it.  I think it is actually better for astrophotography than my T1i...

 

Gives me a couple more days to think about the new camera adapter design,

 

Michael

 

 

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#98 Michael Miles

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Posted 16 September 2014 - 11:31 PM

Reprocessed crop of M27 above.  I like it despite the enlarged stars.  Stacked from 10 frames of 8 seconds at ISO 3200.

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#99 Michael Miles

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Posted 16 September 2014 - 11:44 PM

And a shot of the moon so you can see the field of view with this setup.  I like that the chromatic aberration seems to be so low.  You can also see that the focus is much better than the old pictures.  Still not as good as it is capable of when I get a machined camera adapter though.  You can maybe also see the effect of clouds at the terminator, so that's affecting the sharpness too.

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