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Sharpstar 150mm f/2.8 HNT collimation

Davey-T
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CCD-Freak

CCD-Freak

Posted
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1 hour ago, Gonzo said:

From what I read, the collimation is a bit fiddly at this f/rate, not quite an issue, I guess you just need to be patient and accurate.

What I'd like to know is how often do you really have to redo it? If I get such scope, it will be for my remote observatory which is very remote (I'm talking at least 8 hours drive via several countries...) I would hate having to re-collimate "at every use" really...

The collimation adjustments seem pretty secure so if the scope is handled carefully I don't think it will require much tweaking after travel.  I will know more after I drive 850 miles to New Mexico for a new moon imaging trip.  I am looking forward to using this fast scope under the clear, dry Bortle 1 (SQM 21.99) skies of the NM "boot heel".  

John Love
CCD-Freak
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CCD-Freak
CCD-Freak

I am getting the SS15028HNT dialed in and I  am having fun with it.   I want to try a larger sensor next time I get some clear sky. 120 x 1 minutes  Processed as Lum.  ASI-533MCP   John

CCD-Freak
CCD-Freak

I tried the SS15028HNT with my Canon 100D 18Mega Pixel APS-C DSLR to get an idea of how it would be with a larger sensor.  I am really drooling over the ASI-2600MCP which also has an APS-C sensor.   T

johninderby
johninderby

Is it just me or does this scope seem to be more of a kit to be reassembled properly rather than a finished product. 🤔

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Gonzo

Gonzo

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Dave, I think there is a way to keep the mirror perfectly centre in the cell, however it will require some machining work.

I've found the following thread over in CN where you can see detailed pictures of a Takahashi Epsilon 180ED mirror cell. And from the blog I've linked earlier I do think it might be possible to drill one or two threaded holes on the side of each of the three vertical support, then use some grub screws.

You can use the grub screws to precisely position the mirror dead centre in the cell and of course lock it in.

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Davey-T

Davey-T

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3 hours ago, Gonzo said:

I think there is a way to keep the mirror perfectly centre in the cell,

Hi Stephane, there isn't a problem keeping the mirror centred in the cell, it seems like a perfect fit, rotating the whole mirror assembly on the rear of the tube showed that it wasn't central so adjusted it so that it was using laser in the focuser, the problem seems to be a complete lack of communication between the designer and the people assembling them in the factory, can't expect the guys assembling them to know anything about telescopes but you'd hope there was someone in charge overseeing the work that did.

Now if it would only stop raining it's ready for another test, using DSLR because it's easier to focus using live view.

DSLR-setup.png.2b21a8d74e3a15a263649112430e05ac.png

 

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CCD-Freak

CCD-Freak

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Almost everything in the sample I got is OK....the screws are tight the spider is good and tight and in collimation.  The primary mirror pads on the retaining ring are a bit too thin and not placed close enough to the edge to make proper contact with the mirror edge.   It was easier to fix the pads than fool with sending the scope back for repair which would take way more time and shipping costs.  This was a simple quality control issue and once I get it the way I want it I am documenting what I did and I will send a Message to Sharpstar to make them aware of the issue.   Hopefully they will address it for future customers.  

I think I am really going to like the scope once I get to play with it more.

 

John Love
CCD-Freak
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Hypergraph AP900-3.JPG

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Gonzo

Gonzo

Posted
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12 hours ago, johninderby said:

Is it just me or does this scope seem to be more of a kit to be reassembled properly rather than a finished product. 🤔

That's what this hobby is about really, tinkering... 😂

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CCD-Freak

CCD-Freak

Posted
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9 hours ago, Gonzo said:

Nice simple cable management there John.

 

Thanks....It is a bit more messy down around the power distribution box and the USB hub.   I do try to keep things fairly neat. 🤪

 

John Love
CCD-Freak
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Hypergraph AP900-4.JPG

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CCD-Freak

CCD-Freak

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I am getting the SS15028HNT dialed in and I  am having fun with it.   I want to try a larger sensor next time I get some clear sky.

120 x 1 minutes  Processed as Lum.  ASI-533MCP

 

John Love
CCD-Freak
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B33-Mono-SigmaSum-crop-DN-GR-DDP-curves-2.jpg

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wittmer

wittmer

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HI John

Could you take a picture with a large (full frame) sensor?  I've attached a single frame from the IC1318 and I'm not very happy with the stars at the border. Unfortunately I don't know what I can expect..

King regards

Dominik

IC1318_Light_003_RGB_VNG.png

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Davey-T

Davey-T

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Hi Dominik and welcome to SGL.

If you start back at the beginning of this thread you can see the trials and tribulations that I've had with this scope, there is also a thread on Cloudy Nights discussing them.

I had those little seagull stars across most of the image, the main problem was the primary mirror flopping back and forth in the cell making collimation nigh on impossible.

Did you buy it from TS ? if so I'd simply return it and get them to sort it as they claim to have tested them before dispatch.

Dave

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Davey-T

Davey-T

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6 minutes ago, wittmer said:

I've moved the scope to check if the main mirror is moving, but it seems that I need to remove it to see it.

Dominik

Easy enough to remove, mark it with a bit of sticky tape so it goes back in the same place, remove the ring of screws then rest it on a kitchen worktop with the mirror facing you, hold the scope with one hand and ease mirror ass'y off, swopping hands from side to side and keeping your body in front of it in case it comes off in rush.

When it's off check that all the brackets those screws go into are tight.

Dave

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CCD-Freak

CCD-Freak

Posted
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I tried the SS15028HNT with my Canon 100D 18Mega Pixel APS-C DSLR to get an idea of how it would be with a larger sensor.  I am really drooling over the ASI-2600MCP which also has an APS-C sensor.   This is 60 x 60" (1 hour) @ ISO-800 no filters and I am pretty happy with the result even with a noisy non cooled DSLR.  It was a test but now I wish I had taken Flats.

I am impatiently waiting for more clear sky.

John Love
CCD-Freak
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M42-Cal-Sigma-GR-DN-WB-Sat-Curves-3x3-3.jpg

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Davey-T

Davey-T

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Looking good John, took a few of M42 the other night in Moonlight through thin cloud more to check stars than anything as still a bit off in the corners.
Using ZWO ASI2600MC.

Bought an Optolong L-eNhance filter and made a holder to fit it between the coma corrector and the camera adapter but not had a chance to try it properly, tried an IDAS NBX but it had a thicker surround than normal 2" filter so wouldn't fit.

Dave

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CCD-Freak

CCD-Freak

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I recently got the ZWO filter drawer and it makes putting filters on the SS15028HNT easy.  The above image looks pretty good but the full size image shows a bit of distortion in one corner.  I am getting close to the sweet spot.  I think once I get it exactly collimated it will be easy to keep it there.  The above image was taken after driving about 1200 miles.  I got some adhesive back cork that I will be installing on the ring of the mirror cell this week. 

John Love
CCD-Freak
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Davey-T

Davey-T

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52 minutes ago, CCD-Freak said:

I got some adhesive back cork that I will be installing on the ring of the mirror cell this week. 

I put those layers of felt on mine and it made the mirror too tight and introduced some aberrations on the stars but once it's too tight the adjusters on the retaining ring can be used to get it just right.

Dave

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GalaxyGael

GalaxyGael

Posted
Posted (edited)
On 29/11/2020 at 17:36, Davey-T said:

I put those layers of felt on mine and it made the mirror too tight and introduced some aberrations on the stars but once it's too tight the adjusters on the retaining ring can be used to get it just right.

Dave

Hi @Davey-T, 

Reviving this for a specific query. When your primary was too tight, what star aberrations did you see? Flaring and clipping? 

Edited by GalaxyGael
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Davey-T

Davey-T

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On 06/11/2021 at 08:54, GalaxyGael said:

Hi @Davey-T, 

Reviving this for a specific query. When your primary was too tight, what star aberrations did you see? Flaring and clipping? 

Flaring in the corners as I recall, it took a couple of attempts to get it right not helped by the fact that we never get consecutive clear nights to test anything.

Also tried an assortment of collimation tools including a very expensive Howie Gllatter but found this the best HoTech SCA Laser Collimator with Cross-Hair | First Light Optics
plus a Concentre to accurately align the secondary.

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