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Skymax 180 planetary imaging


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Hi!

This is my second post. I got so much great help in my first post so thank you all :)

I as you know own a skymax 180 on heq5 pro and i have a ZWO asi 120mc camera. I use it only for Lunar and plantary. I currently have 2 barlows: Celestron 2x and 3x.

I feel 3x is too much but on some nights it seems fine. So my question is this: I want to buy a TeleVue powermate and i cant decide on 2x 2.4x 3x 4x or 5x 😛 I really have no clue.. Can someone please help me.. I dont eaven know how much power i can expect from this scope. i have only tried it on the moon but i want the electric focuser and the right televue set up for the oppositions this comming summer.

So please help me guys:)

 

Added some images from tonights lunar session.

Nytt punktgrafikkbilde.jpg

DSO_204925_lapl6_ap193.tif DSO_211245_lapl6_ap38.tif

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I have found that a 1.4x or a 2x Barlow works best with my 180 Mak, 3x is too much.

As the scope is already f15 (more like f16 or f17 if you have extension behind the focuser, eg a flip-mirror), you may find that no Barlow is needed with less bright planets such as Saturn to give the best results.

Chris

 

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Don't use barlow at all, or if you use color camera - you can use x2 barlow but you will need special processing to get proper image size.

With ASI120 - which is camera that has 3.75um pixel size - critical sampling rate is about F/15. That scope is already F/15 scope so no barlow is needed.

Since you have mc version of the camera, to really have that sort of resolution - you either need to use AS!3 and select Bayer Drizzle method of debayering / stacking. This means that if you use PIPP to pre process your movie - check "preserve bayer matrix" option and don't debayer your movie in pre processing.

Other option is to use x2 barlow but then you need special type of processing similar to super pixel mode in regular DSO imaging to convert bayer matrix to color movie at proper resolution - I'm not sure that there is software out there that does that.

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53 minutes ago, Chrb1985 said:

wow its so much i dont know and or understand. So i will get a big enoug image of jupiter and saturn without barlow or powermate?

It is not about size of the image - it is about level of detail.

Aperture of telescope determines what sort of details you will see on a target. In order to record that level of detail with camera you need planet to be of a certain size on chip. Once you reach that size - going any larger than that will have same effect as taking a small image and enlarging it on computer - things get bigger but without any actual detail. There simply is no point in "zooming" further.

In fact - zooming further just hurts your imaging. Making image larger just spreads light over more pixels and each pixel then gets less photons per exposure. Less photons means less signal and that in turn means more noise (or to be precise lower SNR - signal to noise ratio).

For above reasons there is something called critical sampling - imaging resolution after which there is simply no point in going with "more zoom". This resolution is roughly at about 2.4 pixels per airy disk radius for a given telescope. Math behind it is complex, but there are simple rules that you can follow:

pixel size of 2.4um - gives F/11 as scope speed

pixel size of 3.75 gives about F/15

and so on - each pixel size has critical F/ratio (it is fixed F/ratio because with larger aperture you will have more detail so it makes sense to use longer focal length - but ratio of the two remains the same hence - fixed F/ratio for a given pixel size).

Ultimately size of planet on your image with right level of detail (so it does not look blurry) will be determined by scope aperture. Want a bigger planet? Can't do that with barlow - you need a larger scope (once you reach critical sampling of course).

53 minutes ago, Chrb1985 said:

Almost forgot. Can you guys tell me wich camera is best suited for the mak 180?

All cameras are suited to all scopes provided that you can make scope work at F/ratio that is suitable for that camera. In general case this means use of barlow. Only exception to this rule would be over sampling. Then you would need to use focal reducer instead and that one is not as easy because you would need good focal reducer that causes minimal aberrations.

On the other hand barlows rarely cause aberrations (if they are any good) - and you can vary magnification of a barlow element by changing distance to sensor.

When choosing between cameras - you want to pay attention to these things:

1. High QE of sensor

2. Low read noise of sensor

3. Fast download times and use of ROI (region of interest)

These are characteristics that you should be paying attention to. Want the best camera for planetary? Go for ASI385. Too expensive - go for ASI224.

Want to do Lunar and Solar (especially white light with continuum filter from baader or H-alpha)  choose Mono camera - ASI290 for example.

For planets you want OSC camera (one shot color) as you don't need to mess with filters and filter wheels and all of that.

Hope this helps

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2 minutes ago, vlaiv said:

For planets you want OSC camera (one shot color) as you don't need to mess with filters and filter wheels and all of that.

I'd just add to this, if using a colour camera, especially from northern latitudes like Norway, I'd heartily recommend an atmospheric dispersion corrector (ADC).  ADCs counteract the smearing caused by the light from the planet travelling through Earth's atmosphere.  The lower down in the sky the planet is the worse this smearing is.

ADCs can be had for about £130 new or around £100 used.

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17 minutes ago, vlaiv said:

It is not about size of the image - it is about level of detail.

Aperture of telescope determines what sort of details you will see on a target.......

Brilliant explanation and something I've not taken into account during my forays in planetary imaging. Regarding the earlier point about colour cams and Bayer drizzle I may have to reprocess some of my earlier attempts.

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1 hour ago, Chrb1985 said:

ow its so much i dont know and or understand. So i will get a big enoug image of jupiter and saturn without barlow or powermate?

You can use this online Field of View calculator to see hwat the planet will look like with your scope/camera...

https://astronomy.tools/calculators/field_of_view/

 

For example, this is roughly the size of Jupiter with a Skymax 180 (no barlow) and a ASI120 with the ROI set to 640x480...

 

Jup.JPG

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  • 4 months later...

Sorry to hijack this thread, but I was wondering if a HEQ5 mount is enough for imaging planets with the big Mak?

I have the Skymax 127 already, and researching for a suitable mount with room to grow (note that I don't own a car, and I expect to carry the mount two floors to the terrace).

N.F.

 

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On ‎05‎/‎02‎/‎2020 at 00:20, vlaiv said:

Don't use barlow at all,

The best advice.....is just like this.....when you don't have to spend any more money!

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16 hours ago, CraigT82 said:

A skymax 180 will work well on a heq5. That's quite a lump to be carrying up and down stairs though.

 

Even for imaging? That's heartening (I feel that's a bit at the limit, if you add a dual-speed focuser, an OAG and a camera/filters we are nearing 11 kg already).

Maybe the Skymax 150 would be a more realistic scope, I don't know...

Cheers,

N.F.

 

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Planetary type imaging?

Even Eq5 would be sufficient for that - as long as it can carry the weight and point in general direction of a planet - it will do :D

I imaged planets with EQ2 and simple DC motor that even could not track properly - there was potentiometer that regulated tracking speed and I needed to adjust it every 10-20 seconds to keep planet in FOV of camera - but it worked.

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Yes when you see quoted imaging weight capacity for mounts, that's generally deep sky imaging. For planetary your exposures are so short it doesn't really matter if your mount is at its weight limit and a little wobbly. Granted it is always easier if you are well under the weight limit but its really no problem if you're pushing it for planetary. 

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Good to hear (I am sorely tempted to add the Skymax 180 to my arsenal).

A guider is necessary, I suppose? (I have got an old Celestron OAG with my Skymax 127 already).

I wonder, how much sensitive is the 180 to seeing conditions, compared to 127/150? I live 10 km north of Athens center, with lots of concrete roofs around...

Cheers,

N.F.

 

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1 minute ago, nfotis said:

Good to hear (I am sorely tempted to add the Skymax 180 to my arsenal).

A guider is necessary, I suppose? (I have got an old Celestron OAG with my Skymax 127 already).

I wonder, how much sensitive is the 180 to seeing conditions, compared to 127/150? I live 10 km north of Athens center, with lots of concrete roofs around...

Cheers,

N.F.

 

I'm confused here. Are we talking about planetary type imaging with Skymax?

No OAG is needed for that. You don't need guiding. Mount is capable of holding planet in camera FOV even at very small ROI (320x200) - and that is all you need.

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Initially, planetary and lunar/solar imaging are my targets (the latter with a Baader astrosolar film filter).

I might go after small galaxies in the future, like the M31, M51 and M101 (thinking about using the ZWO-ASI178 camera or my already existing Canon 80D for such targets, despite the light pollution here)

 

All this is still 'armchair astronomy', though, as I don't even own a mount (yet).

N.F.

 

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21 minutes ago, nfotis said:

Initially, planetary and lunar/solar imaging are my targets (the latter with a Baader astrosolar film filter).

I might go after small galaxies in the future, like the M31, M51 and M101 (thinking about using the ZWO-ASI178 camera or my already existing Canon 80D for such targets, despite the light pollution here)

 

All this is still 'armchair astronomy', though, as I don't even own a mount (yet).

N.F.

 

I understand.

Yes, OAG is a good option for deep sky imaging / long exposure.

ASI178 is going to be good camera for planetary imaging but not for DSO imaging as FOV is going to be very small.

With such scope, you want as large sensor as possible, so Canon 80D is sensible option. You will want to also look at binning as part of your processing workflow when you start DSO imaging (2700mm FL with almost any pixel size is going to lead to oversampling and you'll want to bin your pixels - in software if needed to circumvent that).

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Forgot to mention that I own also a Canon 6D, so she should be a good match for the 180 (provided that I use a 2" visual back - tried her with the 127 and it was vignetting badly with the Celestron OAG, as the latter is suitable for 1.25", so I will have to use a larger OAG in this case I guess).

N.F.

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