Advice on choosing a camera

[Daniel_Reardon]

Hi all,

I'm new here so here -> http://stargazerslounge.com/showthread.php?t=187736 is my introduction which also introduces the beginning of my dilemma.

I currently have a neximage and have been able to get some images of the moon and planets that I am quite happy with. The moon was taken with a celestron astromaster 130EQ, the planets with an uncollimated 12'' Meade lightbridge (that reminds me I need to seek advice about my collimation issue).

Anyway, I am looking to upgrade from the neximage because while I'm quite happy with the quality, I am not happy with the size of the image. I would ideally like a camera for around $400 but I could be persuaded to stretch that to $500 or even $600 if anyone has an ideal for a great value piece of equipment. I have been investigating the DBK from bintel and the QHY series found here. There are also a couple of different ones at myastroshop.

Any expert advice would be greatly appreciated. I won't be doing any deep sky imaging because I don't have a tracking mount at the moment and so long exposures would not stay on target. I have ordered a Coronado PST (arriving soon) and would like to take images of the sun, moon and planets with this new camera. I have also heard that focussing with the pst can be quite difficult and may require modification of camera or use of a Barlow lens. Any tips here also?

To summarise the main goals for this purpose:

• Making larger Solar and planetary (preferably colour as I don't want to buy a filter wheel) images than the neximage.
  
• Compatible with the Coronado PST if I use a Barlow
  
• Will be good enough to get great images when I upgrade to get a large, tracking APO refactor for imaging.
  
• Possibly suitable for deep sky imaging if price permits (So DSO images can be taken with future APO refractor).
  

All for under $600!!! (as the absolute maximum - $400 preferable).

What do people think about the options outlined ?

Thanks in advance for your advice

- Daniel

[jgs001]

When you say you want to make a larger image... do you mean one you can print larger, or you want to get a larger scale ? As far as I know, the cameras you're looking at, are all approximately the same sensor size as the neximage, which means the print size isn't going to change much. If you're looking to produce a large resultant image (closer in view) you need to extend the focal length of your scope. The 130, is I think, 650mm focal length, and that's not going to produce a large image scale of your target. I'd suggest getting a 2 or 3x barlow and start with that as the first step.

The lightbridge is a longer focal length, but again, for a decent image scale, it's not long enough, and a barlow is a great starting point.

Once you're used to using a 2 or 3x barlow, you can use an extention tube between the barlow and camera to increase the magnification effect.

[Daniel_Reardon]

I did mean print larger. The issue I'm having with the neximage is that, while it says it can record up to 640x480, I read there is compression in anything above 320x280 at 5fps. I was wondering if these other CCDs were capable of doing the 640x480 without compression at a frame rate of ~20fps or more. That would be ideal because without a tracking scope, I don't have much time to collect frames before the image gets out of view.

Thanks

[Cornelius Varley]

If you need a faster framerate look at modern webcams with usb2.0 such as the microcoft lifecam. The camera needs some modifying (removal of the pcb and rehousing) which isn't too complicated instructions. The pcb can be rehoused in a custom made container such as this one or a suitable eyepiece/barlow barrel.

Peter

[Daniel_Reardon]

That sounds good, but I'm not really into the DIY stuff, I'd rather just buy a ready-to-go astrophotography CCD camera

[jgs001]

the difficulty with printing large, you need more pixels. That leads, generally to larger sensors, making the image scale smaller...

The neximage, I think, is similar if not having the same internals as the SPC900 webcams, and they can do 10 fps which I believe is without compression, 15 if you're lucky, at 640x480.

The Imaging Source cameras seem able to rattle off very high frame rates, with the same size sensor. I use a QHY5v as a guider and a lunar/planetary imager, and can get frame rates of around 30 fps on average (although that depends on how far I'm trying to push things for image scale with barlows), which also has a similar sensor size. (VGA 640x480 ish).

[Daniel_Reardon]

the difficulty with printing large, you need more pixels. That leads, generally to larger sensors, making the image scale smaller...

Ahh... Okay, does the scale decrease linearly with sensor size?

[jgs001]

It's not that it makes the image scale smaller per se... the size of the target on the sensor remains the same, but you end up with a lot of wasted pixels on the larger sensor, so if you crop to the same picture size, you still can't print any larger.

I think my earlier statement was a bit confusing....

To print large, you need lots of pixels... therefore, either a larger sensor of the same size pixels, or cram more pixels into the same size sensor, which can lead to more noise.

You're better off, making the focal length longer, to increase the focused target size on the chip, than trying to get more pixels I think.

[Daniel_Reardon]

Okay then, so how about the DBK which claims to do 60fps at 640x480. I've heard good things about the image quality too.

[jgs001]

I've heard good things about the IS cameras... DBK, DMK, DFK... not sure what they all mean/are mind... but ...

[libraryman]

There is a Lifecam and adapter for sale on A B & Sell at the moment!

Ray

[Daniel_Reardon]

Sorry Ray, what's "A B & Sell"?

thanks.

I'll also like to extend this question to how important a Barlow will be when trying to take images with the Coronado PST. I have a 2x Barlow that I got with the Celestron eyepiece and filter kit, I was wondering if this will be sufficient or whether it's worth spending $150 on the Celestron ultima APO Barlow - that thing looks nice!

[jgs001]

Daniel, AB&S is Astro Buy and Sell... I know of the UK one, but I don't know if there's an Aus one, or whether you'd be able to access it.

[libraryman]

OOps, sorry Daniel, i didn't look at your location down under.

Ray

[Daniel_Reardon]

OOps, sorry Daniel, i didn't look at your location down under.

Ray

haha that's okay, I found an Australian equivalent as a result! Now I can spend even more hours window shopping.

[ollypenrice]

Nobody's mentioned that you are asking for the impossible! Your PST will pass near monochromatic light in the deep red. If you use a colour camera to capture this light only one pixel in four will be operating since the two greens and one blue of the colour matrix will block the light. On small chips going down to one in four cannot be a good idea.

I use a mono DMK21 for solar imaging. I'd like the bigger chip of the 41 but the camera is simply superb.

Olly

[Daniel_Reardon]

That would be fantastic but I want to use it for planetary imaging too. I don't think I'm ready to use a filter wheel. Is there a cheaper option? I have red, green and blue filters from a celestron eyepiece and filter kit, are they the right ones to combine to get a natural colour?

Cheers,

- Daniel

[ollypenrice]

Only the option of having colour and monochrome webcams. There is no way out of the fact that using a colour camera in an Ha scope is 25% efficient. That is never going to change.

Olly

[Gina]

Could I be right in thinking the QHY5 is about the cheapest mono camera? It has a half inch image sensor too which I think would well cover the sun's disc.