24 replies to this topic

[Spaceman 56]

hello imagers.

 

I am new to astrophotography, but have been able to get some good results, mainly due to my Bortle 1 location in New Zealand.

 

I have a Stellarvue 80mm Doublet refractor, and Focal reducer 0.80, and my camera is a Nikon D5600. I plan to keep those for a while.

 

I have been shooting Unguided subs at 30 seconds exposure time and ISO-400, and stacking using Siril.

 

Many people say I need a Guide Scope, to take longer Subs, and I see the following options.

 

1. ZWO ASi-120MM-S

it has 1280 by 960 pixels and pixel size is 3.75

 

2. ZWO-ASI-290MM

it has 1936 by 1096 pixels, and pixel size is 2.9

 

3. ZWO-ASI-174

it has 1936 by 1216 pixels and pixel size is 5.86

 

the Cost differance between 1 and 2 is not much, but number 3 is much more expensive.

 

can anyone advise what would be Better ?  and WHY ?

 

thanks Spaceman

[Ljubo]

2) is more sensitive then 1), but if you have Bortle 1 skies, it wouldn't mean much.

3) is good if you have trouble finding good guider star (and is used in an OAG configuration, mostly), but then again you don't have that problem with your combo.

 

Bottom line: buy 2) if you want to be more sure (or use long focal length guide scope). Otherwise, 1) is quite enough for your needs.

[michael8554]

Any of those cameras would be suitable with the right FL Guidescope (for Off Axis Guiding you should opt for the most sensitive).

 

You haven't said what the FL of your guidescope is ?

 

The imaging scale with your Nikon D5600 is 1.79arcsec/pixel.

 

I would suggest a guide image scale of no bigger than 5arcsec/pixel.

 

So a basic 60mm f/4 guidescope would work with any of those cameras.

[barbarosa]

My guide camera is an ASI290 mono. Before that I used an ASI120 mono. I've used both cameras in 50mm guide scopes of  two different focal lengths to guide a C-9.25, a TV-85 w/wo the TV reducer and an 120mm f/7. And for what it might be worth I also used both cameras and the TV-85 as a guider for a C-11 (just because I could and it gave me a chuckle to use the TV-85 and a cheap camera for guiding. Actually it made sense. The TV-85 was piggy back on the C-11 and at the time I did not have a useful small guide scope. 

 

The point is that they all worked. The current guide scope is a SW RACI finder with the prism and eyepiece holder removed and an SCT male thread to M42 male thread adapter, plus and extension ring screwed on to get the camera in focus. It is light weight and works fine.

[Spaceman 56]

Any of those cameras would be suitable with the right FL Guidescope (for Off Axis Guiding you should opt for the most sensitive).

 

You haven't said what the FL of your guidescope is ?

 

The imaging scale with your Nikon D5600 is 1.79arcsec/pixel.

 

I would suggest a guide image scale of no bigger than 5arcsec/pixel.

 

So a basic 60mm f/4 guidescope would work with any of those cameras.

hi Michael.

 

I have not bought a guidescope yet, but thought the Camera selection would help select the guidescope?

 

I dont understand Arc/pixels or imaging scale.

 

what does the 1.79 arctic/pixel for the Nikon D5600 mean?

 

if its very complicated I won't get it. I am pretty old and not super technical.

[maheitka]

Hi spaceman

 

I use the 290 for my refractor (350mm focal length) and a 174 for my reflector (2000 mm focal length), due to their pixel size. Both work perfectly!

 

CS

[michael8554]

if its very complicated I won't get it.

 

In that case just get a basic 60mm f/4 guidescope and the ZWO ASI-120MM-S and you're good to go :->

Edited by michael8554, 26 June 2022 - 04:34 AM.

[barbarosa]

There are rules of thumb, formulae, customs and some science telling us how to select the ideal guide scope objective size and focal length to match the main the imaging scope. Like wise there are similar things for matching the camera sensor size and pixel size , well you get the drift.  Ignore it.

 

The advice in the post above will work just fine, but so will any scope sold as a 50mm or 60mm guide scope or one of the mini guiders like the ZWO  or SV Bony 30mm f/4 Mini Guide Scope . For your refractor I would go with the mini.

[Der_Pit]

Hmm, as he intends to stay with his 80mm I'd say a 60mm guider is oversized....

I'd rather get something smaller, and put the saved money in a 290MMmini instead of the 120....

[james7ca]

If you plan on staying with the 80mm and 0.8X reducer then I agree with Der_Pit and David, get a small 30mm, f/4 guide scope and the ZWO ASI290MM. That's what I'm using on my 0.8X reduced Stellarvue 80mm APO (resulting effective focal length of the Stellarvue is 384mm).

 

Below is a picture of a SVBONY, 30mm, f/4 guide scope with an ASI290 camera mounted to my Stellarvue 80mm APO. Note, you can save some money by getting the USB2 version of ZWO's IMX290, that's their mini guide camera that has a 1.25" housing. I went with the standard USB3 version because it makes for a more compact setup once attached to the guide scope (as shown below).

 

The only issue I've had with the SVBONY is that it has a very short (almost non-existent) dew shield. So, I just took some sheet neoprene and made a slip-on dew shield. I haven't even needed to use a dew heater on the guide scope because the objective is so small and thus is well protected by my self-made dew shield (the neoprene probably also insulates the metal around the objective).

Attached Thumbnails

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Edited by james7ca, 26 June 2022 - 05:25 AM.

[acrh2]

I'm with james7ca on this one.

 

I have both the Svbony and the ZWO 30/120 F4 mini guide scopes paired with ZWO ASI120MM-S,  and they work very well up to 1400 mm focal length. Guiding at about 0.5 arcsec RMS total error (0.4 on a good night.)

 

ZWO ASI120MM-S or ZWO ASI120MM Mini cameras should also do the trick.

[Spaceman 56]

Note, you can save some money by getting the USB2 version of ZWO's IMX290, that's their mini guide camera that has a 1.25" housing. I went with the standard USB3 version because it makes for a more compact setup once attached to the guide scope (as shown below).

 

 

thanks James. exactly the info I need.

 

regarding the USB2 and USB3 options, I have seen statements from ZWO on their website saying that the USB2 versions are NOT

 

RECOMMENDED for MAC users, for some reason, and that the USB3 ones are OK for Mac.

 

anyone else know anything about all that? 

Edited by Spaceman 56, 26 June 2022 - 03:49 PM.

[Spaceman 56]

this is from ZWO spokesperson

 

[hollo]

thanks James. exactly the info I need.

 

regarding the USB2 and USB3 options, I have seen statements from ZWO on their website saying that the USB2 versions are NOT

 

RECOMMENDED for MAC users, for some reason, and that the USB3 ones are OK for Mac.

 

anyone else know anything about all that? 

USB2 is slow at transferring data compared to USB3.

 

To try and work around this ZWO cheated and didn't follow the USB spec on the USB2 versions of some of their cameras. When you don't follow the spec it is unpredictable whether things are going to work, and so you need to test it out. Apparently they did all their testing on windows, and delivered a camera with nice fast download speeds, that didn't follow the USB spec, but Windows didn't mind. Unfortunately MacOS and Linux did.

 

Recent posts on Linux suggest that these cameras now work OK. I don't know about on Mac, but would hope that they've also fixed the problem there.

[bobzeq25]

hello imagers.

 

I am new to astrophotography, but have been able to get some good results, mainly due to my Bortle 1 location in New Zealand.

 

I have a Stellarvue 80mm Doublet refractor, and Focal reducer 0.80, and my camera is a Nikon D5600. I plan to keep those for a while.

 

I have been shooting Unguided subs at 30 seconds exposure time and ISO-400, and stacking using Siril.

 

Many people say I need a Guide Scope, to take longer Subs, and I see the following options.

 

1. ZWO ASi-120MM-S

it has 1280 by 960 pixels and pixel size is 3.75

 

2. ZWO-ASI-290MM

it has 1936 by 1096 pixels, and pixel size is 2.9

 

3. ZWO-ASI-174

it has 1936 by 1216 pixels and pixel size is 5.86

 

the Cost differance between 1 and 2 is not much, but number 3 is much more expensive.

 

can anyone advise what would be Better ?  and WHY ?

 

thanks Spaceman

 

 

This is easier than you think, the choice of camera is not all that critical.  PhD2 is very good at handling all kinds of cameras.  You do have to pay attention to one other thing.

 

I've used all three cameras.  I've used the 120MM quite successfully with a guide scope.  Many have.  The others are a bit better (more sensitive) but it's no big deal.  I got them to use with an off axis guider, which is more demanding than a guidescope.

 

CRUCIAL is to mount the guide scope securely, in 2 rings.  Guiding does little good if the guide scope tracks, and the main scope does not follow precisely.  Using a finder shoe is the usual reason for that.

 

I have a Nikon D5600.  I recommend ISO 200 (more dynamic range), and 120 second subs (long enough).  Sample.

 

https://www.astrobin.com/263253/J/

 

The more subs, the better.  My general principal.  One hour total (30 subs) minimum, two is better, four good.

Edited by bobzeq25, 26 June 2022 - 04:54 PM.

[bobzeq25]

Hmm, as he intends to stay with his 80mm I'd say a 60mm guider is oversized....

I'd rather get something smaller, and put the saved money in a 290MMmini instead of the 120....

And I'd rather mount the guidescope securely, and not worry about the specific guidescope or camera.  That's more important.

[acrh2]

And I'd rather mount the guidescope securely, and not worry about the specific guidescope or camera.  That's more important.

His guide scope shoe has two screws. The total weight of Zwo guide scope+camera is 350g. A little more for Svbony.

I think he will be ok.

 

 I use this combo guiding 1400 mm Mak with a single screw shoe - 4 min subs, round stars.

 Unlike the 50 mm Orion guide scope, which produced slightly elongated stars. 

[Spaceman 56]

 

I have a Nikon D5600.  I recommend ISO 200 (more dynamic range), and 120 second subs (long enough).  Sample.

 

https://www.astrobin.com/263253/J/

 

 

once I get that guide scope and then get PHD2 going, I will try for those 2 minute subs.

 

30 seconds is about all I can run now.

 

Spaceman

[Oort Cloud]

The 174mm mini just went on sale again...it went from $600 to $500 and now $400. I just bought one last night so I can use my 462mc as a dedicated planetary cameras and have the 174mm mini as a dedicated guider.

[Spaceman 56]

The 174mm mini just went on sale again...it went from $600 to $500 and now $400. I just bought one last night so I can use my 462mc as a dedicated planetary cameras and have the 174mm mini as a dedicated guider.

where Mr Oort ?

[Skysmacker]

where Mr Oort ?

AegenaAstro

 

https://agenaastro.c...ing-camera.html

[acrh2]

It seems to me that ASI174 was designed specifically for guiding with OAG with those huge pixels.

Probably not that great for guiding with a small guide scope.

[Spaceman 56]

AegenaAstro

 

https://agenaastro.c...ing-camera.html

Dam its the USB-2 version.

 

apparently they don't work on Mac

[Spaceman 56]

It seems to me that ASI174 was designed specifically for guiding with OAG with those huge pixels.

Probably not that great for guiding with a small guide scope.

thanks Acrh2.

 

I don't want to screw it up with the wrong camera.

 

I like your earlier suggestions.

[Oort Cloud]

where Mr Oort ?

Agena, Highpoint, Opt