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Planning for the future - FOV


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So far, I have the WO61, Askar 135 and Askar 200 on the way.

I think that with a couple of Powermates for use with the 61mm, I can get a nice, graduated FOV to take images.

I think that I can get 2minute+ exposures from my mount with guiding so exposure length might be do-able at longer focal lengths.

Does this sound like a good idea or would a bigger scope and better mount be the way to go for smaller frame size?

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5 minutes ago, newbie alert said:

So you're planning to do planetary imaging?

You don't need 2 min exposures for planetary.. lucky imaging is the preferred way

The moon is just for scale. DSOs are really my thing.

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You don't want a Barlow for deep sky .. the tools you have are for widefied and you can frame targets like North American, m31  nicely with them... If you use a Barlow it will soften the image and you will need far more exposure time

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12 minutes ago, newbie alert said:

You don't want a Barlow for deep sky .. the tools you have are for widefied and you can frame targets like North American, m31  nicely with them... If you use a Barlow it will soften the image and you will need far more exposure time

Thanks.

So I will get no advantage from powermates? The way to go - something like a HEQ-5 and 130 PSD do you think?

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Definitely bigger scope and mount. Pawermates or barlows will just l mean imaging above F10 which is really no good for deep sky. I think 400mm is a pretty good FL for an awful lot of stuff and the next step is looking towards galaxy imaging. Maybe and HEQ5 and RC6 with reducer?

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So I have been thinking about this an I have realised that the problem I have isn't a FOV problem, but an under-sampling problem.

The camera I have has pixel size of 5.76 um which is far too big for any of the scopes I use. As I see it, I have 4 options:

1. Get a mount/scope setup which more closely suits the pixel size of my camera. As suggested by @Clarkey above. That would cost at least £1500.

2. Get a x2 powermate/barlow lens. Much cheaper than option 1 but unworkable due to having F10+

3. Get a camera with a smaller pixel size - ZWO ASI 178 might be a good solution.

4. Give up and take up Golf instead,

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On 20/05/2022 at 21:26, Clarkey said:

Golf is expensive and even more frustrating and pointless than AP

Unbelievable though it may seem, we have visitors who do BOTH. Just imagine that: pointless squared🙃.

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On 20/05/2022 at 17:19, Astro Noodles said:

So I have been thinking about this an I have realised that the problem I have isn't a FOV problem, but an under-sampling problem.

The camera I have has pixel size of 5.76 um which is far too big for any of the scopes I use. As I see it, I have 4 options:

1. Get a mount/scope setup which more closely suits the pixel size of my camera. As suggested by @Clarkey above. That would cost at least £1500.

2. Get a x2 powermate/barlow lens. Much cheaper than option 1 but unworkable due to having F10+

3. Get a camera with a smaller pixel size - ZWO ASI 178 might be a good solution.

4. Give up and take up Golf instead,

Don't worry about sampling, those  sampling tools aren't accurate and won't impeade the images you get.. the largest you will see is on your laptop... You can drive yourself bonkers chasing that perfect setup according to the tools and then won't look have as good as another that's hugely undersampled... 

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On 20/05/2022 at 17:19, Astro Noodles said:

3. Get a camera with a smaller pixel size - ZWO ASI 178 might be a good solution.

Don't bother with the ASI 178, it's not cooled and OSC to boot. If you want a new camera (And everyone could use a new camera LOL) then go for one with set-point cooling. At one time I would have insisted on mono, but the latest batch of CMOS OSC are worth a look.

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Posted (edited)

I've seen on astrobin some pleasing galaxy image taken with a 61mm telescope and a planetary camera, I searched under ASI462MC as imaging camera. I go on if it pleases me that's all I aim for. 

(It's not necessarily a good approach, depends on what you are after and aim to achieve, or what may already own)

Edited by happy-kat
Typo
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Posted (edited)

I always think it best to start with the object you want to image.

1) It has to fit on your chip unless you're up for a mosaic. Field of view is controlled by focal length and chip size so balance the two to fit your needs. (Big expensive scope and big expensive chip or vice versa!)

2) The object needs to be properly sampled to be viewable at full size. I think this is pretty flexible. You get a nice 'look' up to 3.5 arcsecs per pixel and, below about 1.5"PP you are probably oversampling and losing speed. (If you're doubtful about 3.5"PP check the APOD records because the Kodak 11 meg plus Tak FSQ106 has more APODS than you can shake a stick at.)

3) Remember that speed isn't determined by F ratio, it's determined by the relationship between area of aperture and area of pixel. What matters is 'aperture per pixel.'

So, first of all, what exactly do you want to image? One rig cannot do all.

Olly

Edited by ollypenrice
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1 hour ago, ollypenrice said:

So, first of all, what exactly do you want to image? One rig cannot do all.

Thanks Olly.

I haven't really decided on any specific targets. I want to see smaller things more clearly. So I suppose better images of the Crab nebula and similar things and some of those galaxies in Leo.

Ultimately, It is my aim to have a collection of scopes which are suitable for imaging at all/most scales, but I'm anticipating a timescale of a decade or more. At the moment I am having plenty of fun with my widefield setup.

At the moment, my camera is bumping near to 3.5 arc seconds per pixel with my WO 61. So, in order to move forward, I need more aperture, but the pixel size of my current camera is fine for that (4.29um) ? Makes sense. Next year perhaps.

 

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Posted (edited)
19 hours ago, newbie alert said:

Don't worry about sampling, those  sampling tools aren't accurate and won't impeade the images you get.. the largest you will see is on your laptop... 

I've recently discovered I can connect wirelessly to my smart TVs and 'throw' my images over for display. One is a 32" and the PNG images look stunning. They get a bit too grainy on the 65" but viewed from a distance look fine.  The interesting thing is they show that my laptop display needs colour calibrating. 

Graeme 

Edited by jacko61
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