Celestron X-Cel LX 2X vs Televue Powermate 2.5X (or 2X)

[Maideneer]

Hi gang, I'm only an intermittent year into AP so I don't have too much experience yet but I do ok with planetary imaging which is where my focus is right now. I operate a C925HD with an ASI224. On my image train, I've got my 224 going into an ADC which goes into a 2X Celestron X-Cel LX with an IR/UV Cut threaded in + a flip mirror. It's really the first time I'm using a barlow for AP so I wasn't sure if I was doing things right. It was a perfectly clear night out but Saturn kept coming out blurry, I must have focused and refocused a hundred times, even used a Bahtinov on a star and then slewed back over just to make sure. I'm guessing the seeing wasn't great as it was very humid out, but isn't that any summer night really? Of course I know barlows affect birghtness so I had to pump the gain a little bit, but focusing proved impossible.

From my understanding, you want 5 times the pixel size of the camera to get an optimal performance out of my focal ratio (native f/10). So the ASI224MC has 3.75 micron pixels, so I should be aiming to produce a focal ratio of around 5x3.75 = f/18.75. My 2x barlow basically achieves that...wonderful, great!

I just don't know if the 2X I'm using is of a good enough quality or if I was doing something else wrong. Would this famed Powermate I always hear about improve quality by a large degree? If it does, the 1.25" version they have is a 2.5X which would make my focal ratio f/25, way surpassing the 18.75 that if generally optimal for my setup, is that ok?  But they do have a 2" version with a 1.25" adapter that is 2X and not 2.5X, which would bring things down back to f/20 again which is closer to the range I need (I think).

Not sure how to proceed and I could use advice.  I'm not the most technical person on earth, so try not to get too into the weeds with technical info please.

Side note - I think I need a new IR/UV filter, the glass is loose on mine so I think it dislodged...advice on a decent one of these would help me too.

[Zeta Reticulan]

I don't know anything about AP. But this Altair tele-extender might be the solution. 

I have the 3x version. It's very probably sold under a different brand name in the US. Explore Scientific have something similar. They are probably made in the same Chinese factory lol.

[Don Pensack]

4 hours ago, Maideneer said:

Hi gang, I'm only an intermittent year into AP so I don't have too much experience yet but I do ok with planetary imaging which is where my focus is right now. I operate a C925HD with an ASI224. On my image train, I've got my 224 going into an ADC which goes into a 2X Celestron X-Cel LX with an IR/UV Cut threaded in + a flip mirror. It's really the first time I'm using a barlow for AP so I wasn't sure if I was doing things right. It was a perfectly clear night out but Saturn kept coming out blurry, I must have focused and refocused a hundred times, even used a Bahtinov on a star and then slewed back over just to make sure. I'm guessing the seeing wasn't great as it was very humid out, but isn't that any summer night really? Of course I know barlows affect brightness so I had to pump the gain a little bit, but focusing proved impossible.

From my understanding, you want 5 times the pixel size of the camera to get an optimal performance out of my focal ratio (native f/10). So the ASI224MC has 3.75 micron pixels, so I should be aiming to produce a focal ratio of around 5x3.75 = f/18.75. My 2x barlow basically achieves that...wonderful, great!

I just don't know if the 2X I'm using is of a good enough quality or if I was doing something else wrong. Would this famed Powermate I always hear about improve quality by a large degree? If it does, the 1.25" version they have is a 2.5X which would make my focal ratio f/25, way surpassing the 18.75 that if generally optimal for my setup, is that ok?  But they do have a 2" version with a 1.25" adapter that is 2X and not 2.5X, which would bring things down back to f/20 again which is closer to the range I need (I think).

Not sure how to proceed and I could use advice.  I'm not the most technical person on earth, so try not to get too into the weeds with technical info please.

Side note - I think I need a new IR/UV filter, the glass is loose on mine so I think it dislodged...advice on a decent one of these would help me too.

Your issue is Seeing.

The magnification you seek to achieve requires exceptionally good Seeing, and a mount that can deal with such a long focal length and still track smoothly.

I regularly observe where there is excellent seeing, but even then, the planetary imagers take a hundred thousand images to get 500 good ones for stacking.

You might be better taking a video and then using software to reject the images that are too far from average focus to combine.

And that assumes your scope is cooled down, which might be the issue.

If it has sat out the entire night and you are taking images after many hours of the scope sitting outside, the optics are probably cooled.

If not, heat in the scope itself could be blurring the image.

And when was the last time you checked collimation in the scope?  A very high power star collimation might help.

 

And, were the planets being imaged still low in the atmosphere, or did you wait for Saturn to culminate (cross the meridian)?

Because getting a sharp image when the planet is below 30° altitude is iffy, and below 20° is just plain unlikely.

 

But, all that being said, try every morning for many days in a row, and you may find one of those mornings has better seeing.

Take a lot of images, then.

[Maideneer]

9 minutes ago, Don Pensack said:

Your issue is Seeing.

The magnification you seek to achieve requires exceptionally good Seeing, and a mount that can deal with such a long focal length and still track smoothly.

I regularly observe where there is excellent seeing, but even then, the planetary imagers take a hundred thousand images to get 500 good ones for stacking.

You might be better taking a video and then using software to reject the images that are too far from average focus to combine.

And that assumes your scope is cooled down, which might be the issue.

If it has sat out the entire night and you are taking images after many hours of the scope sitting outside, the optics are probably cooled.

If not, heat in the scope itself could be blurring the image.

And when was the last time you checked collimation in the scope?  A very high power star collimation might help.

 

And, were the planets being imaged still low in the atmosphere, or did you wait for Saturn to culminate (cross the meridian)?

Because getting a sharp image when the planet is below 30° altitude is iffy, and below 20° is just plain unlikely.

 

But, all that being said, try every morning for many days in a row, and you may find one of those mornings has better seeing.

Take a lot of images, then.

Probably below 20 degrees was my problem so I'm going to start there.  Collimation is perfect! I actually have my scope & mount always sitting in the garage so it's constantly used to the humidity and atmosphere of the outside world.

I do in fact take videos as you say, SER files through Sharpcap and then stack with AS3. 

Appreciate the tips, I'll work on it!