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Advice on a little telescope for the Star Adventurer


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1 hour ago, ollypenrice said:

The idea that focal length and chip size are related is an error imported from the daytime camera world via something called 'crop factor.' I would ignore all this completely. It is utterly meaningless. Keep it nice and simple in astrophotography and you won't go wrong. You have a focal length, determined by your scope's optics. This is a simple and non-negotiable fact. You have a chip size of x by y, also non negotiable. Then you have your pixel size, which (allied to you focal length) specifies your resolution in arcseconds per pixel. Your chip size simply speciifies how much sky you cover. It has absolutely no effect whatever on your resolution. (That derives from focal length and pixel size. The number of pixels you have is also irrelevant.)

Olly

Edit: Crossed with Adam J but we are saying the same things.

Really appreciate your input and explanation Olly. Very insightful and good to know! Thanks for your knowledge :) its so very helpful to get me on the right track. 

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1 hour ago, ollypenrice said:

I would look at it this way: the mount has a maximum payload and a maximum tracking accuracy. Both, not just one, have to be respected. Payload is obviously easy - you just weigh what you are putting on the mount. Accuracy is more difficult. The unit that matters is resolution measured in arcseconds per pixel. This value is derived from focal length and pixel size, so focal length alone is not a useful term. (Long focal length with big pixels equals short focal length with small pixels in terms of resolution, stating it simply.)

I think that the best information will come from published images in which the user states what camera, at what focal length, was being used. To turn this into arcseconds per pixel you can use a number of online calculators such as this one: http://www.12dstring.me.uk/fovcalc.php

Olly

Thanks again Olly. Very much appreciated 

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38 minutes ago, fireballxl5 said:

shout out for the versatility of the light-weight Tak FS60CB system - some images for your consideration at 252mm (reducer @ f4.2), 366mm (flattener @ f6.1) and 610mm (1.7x extender with flattener ~f10). Admittedly used on an AstroTrac rather than the SA...any excuse to post some of my photos :biggrin:

HTH, Andy

 

Antares & Rho Oph - FS60CB f4.2.jpgAntares & Rho Oph F4.2

NA & Pelican - FS60CB f6.1.jpgNA and Pelican @ F6.1

M20_M8 - FS60CB f10.jpgM20 @ F10

2017 Solar Eclipse - FS60CB f10.jpgSun & Moon F10

Thanks Andy! Fantastic pics!! :) 

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This is what I managed with a WO ZS61 & a full frame nikon D810 on the star adventure, not a great image i know but it will give you some idea of what you can expect regards field flatness you would be better off leaving your sony in full frame mode and crop later if required. 

LR M31 Stacked 18m12s 18frames iso3200-2.JPG

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Regarding my images using the Tak FS60CB, I should add that these images were taken using a crop Canon 40D (astro modified). Pixel scales as measured at http://nova.astrometry.net are as follows:

252mm, 4.59 arcsec/pixel

366mm, 3.14 arcsec/pixel

610mm, 1.86 arcsec/pixel

HTH, Andy

 

Edited by fireballxl5
minor numerical typo
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A bit late to the party, so you may already have everything in place, but you're right in that you'll need the M48 to T2 adapter plus the T2 to Sony E adapter. What I found through this setup was that my overall spacing from lens to sensor was too long by just over 12mm. Spacing sees very important on this setup. With my mirrorless A6000 I had to replace the end part of the Flat61 (essentially a 20mm extension tube) with a 7.5mm piece to get the right distance. I can swap this out for a LP filter if required.

The ZS61 plus the Star Adventurer seems like a great combo that does allow for future guiding if you require slightly longer exposures, but given you're on Sony you may be limiting them anyways.

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On 11/10/2017 at 22:30, AdamT said:

This is what I managed with a WO ZS61 & a full frame nikon D810 on the star adventure, not a great image i know but it will give you some idea of what you can expect regards field flatness you would be better off leaving your sony in full frame mode and crop later if required. 

LR M31 Stacked 18m12s 18frames iso3200-2.JPG

Great image Adam :) 

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On 18/10/2017 at 14:40, agthomson said:

A bit late to the party, so you may already have everything in place, but you're right in that you'll need the M48 to T2 adapter plus the T2 to Sony E adapter. What I found through this setup was that my overall spacing from lens to sensor was too long by just over 12mm. Spacing sees very important on this setup. With my mirrorless A6000 I had to replace the end part of the Flat61 (essentially a 20mm extension tube) with a 7.5mm piece to get the right distance. I can swap this out for a LP filter if required.

The ZS61 plus the Star Adventurer seems like a great combo that does allow for future guiding if you require slightly longer exposures, but given you're on Sony you may be limiting them anyways.

Thanks for the input. I am indeed all 'in place'. Scope arrived last week, now just need some clear skies for testing! 

It balances great on the SA with the Orion Guidescope. Just the right size and focal length for a beginner like me and a great grab and go setup (decent skies are an hours drive for me) Thanks for everyone's input :) 

IMG_1335.JPG

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On 18/10/2017 at 15:02, happy-kat said:

If you have the sony a7s from what I've seen don't update the firmware, you'll lose any benefit on long exposure imaging. Sony and their infamous star eating issue on exposures over 30 seconds.

Funnily enough I have never updated the firmware on my A7S. I'm still on v1.10.

Does this mean I don't have the dreaded star eater algorithm? I was under the impression it affected all the cameras from day dot. I wasn't aware it was 'introduced' in a later firmware update? I'd like to be wrong about this one... ! 

 

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1 hour ago, Astro Buer said:

Thanks for the input. I am indeed all 'in place'. Scope arrived last week, now just need some clear skies for testing! 

It balances great on the SA with the Orion Guidescope. Just the right size and focal length for a beginner like me and a great grab and go setup (decent skies are an hours drive for me) Thanks for everyone's input :) 

IMG_1335.JPG

Have you got any pics of it all set up with the guide scope?

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On 19/10/2017 at 20:18, AdamT said:

Have you got any pics of it all set up with the guide scope?

Sorry it's taken me a little while to get this image up! Here's the setup with the guide scope attached.

This is with the clutch open so it's well balanced :) 

IMG_1354.JPG

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  • 3 years later...
On 26/10/2017 at 00:17, Astro Buer said:

Sorry it's taken me a little while to get this image up! Here's the setup with the guide scope attached.

This is with the clutch open so it's well balanced :) 

IMG_1354.JPG

I should thank you for the nice and informative discussion thread. Can I ask the total weight excluding the counter weight and the guide scope? I mean only camera+telescope+flatteners and extention tubes. Do you have any experience of how SA performed with/without guiding? Thanks a lot in advance.

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