4 replies to this topic

[RodgerDodger008]

Very windy conditions last night on ground level and also fairly strong jet stream so not ideal. 

 

First light with ADC and hoping some of you can help me with my understanding of how to use it more effectively.

 

It seemed like with the ADC required gain goes up considerably and obviously so does noise. Must say did not expect to have to increase gain as much as it did.

 

The ADC also added quite a bit to the focal ratio, definitely too much for the seeing I was having. No ADC = 12.9 (+2x barlow) with ADC = 16.4 (+2x barlow), need to be around 14.5 to be ideal. 

 

Wondering if I should skip the barlow when using the ADC. 

 

Anyway the images are not great but probably better than expected, not sure if the ADC helped or hindered last night but certainly learnt quite a bit during the session.

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Edited by RodgerDodger008, 26 November 2022 - 09:48 PM.

[Kokatha man]

I prefer to go a bit less than the "5x" pixel sizing that gets spruiked ad infinitum & I don't know what you mean by increasing the gain significantly...perhaps you mean that because of the greater image scale you have to work at with the ADC means you need more gain for the same histogram..?

 

In any case a couple of things - make sure that you increase the integration time for the ADC display balls if you use that approach, it stops them ricocheting around like crazed pin-balls.

 

I've posted plenty of examples of how to utilise just the barlow's lens element minus the body to reduce any specific barlow's amplification factor - using a T2 male-female adaptor in the train only requires the lens element to be "floating" and held via the aforementioned device's compression band clamps.

 

Here's my extrapolation of the Televue 2x barlow's response where with just the lens element it can provide almost down to 1.25x without any deleterious optical effects. There are of course specific lower-amplification barlows available as alternatives...

 

Btw we've found that an ADC can still provide correction with Jupiter in Sthn. Oz this year at 55° or so...

 

 

If you look at our current thread you will see the imaging train I use - this has a custom Siebert 1.5x barlow but you can hold a "floating" barlow lens element in that T2 male-female adaptor that is connected to the rear of the EFW shown - a main concern is to have rotational capabilities for the camera as well as for the ADC for initially setting it level.

 

Mars definitely benefits from using an ADC in Oz for us folks nowadays!

 

This old thread of mine that someone revived recently is probably worth a good look to give you some ideas. https://www.cloudyni...owers-anyone/  

 

 

[RedLionNJ]

 

It seemed like with the ADC required gain goes up considerably and obviously so does noise. Must say did not expect to have to increase gain as much as it did.

 

The ADC also added quite a bit to the focal ratio, definitely too much for the seeing I was having. No ADC = 12.9 (+2x barlow) with ADC = 16.4 (+2x barlow), need to be around 14.5 to be ideal. 

 

That's quite an increase in focal ratio (27%) - and accounts perfectly for the need to increase either the gain or the exposure to keep the histogram the same as when not using an ADC as you're now spreading the light out over that many more pixels.

 

Difficult as it may be to physically (and psychologically) achieve, I'm with Darryl on the smaller focal ratios. The vast majority of the time, imaging at somewhat less than the apocryphal "5x pixel size" will yield better-looking results.

[RodgerDodger008]

I prefer to go a bit less than the "5x" pixel sizing that gets spruiked ad infinitum & I don't know what you mean by increasing the gain significantly...perhaps you mean that because of the greater image scale you have to work at with the ADC means you need more gain for the same histogram..?

Thanks Darryl, great all round advice and yes I suppose in retrospect that is what I meant.

Will play around with my imaging train and try reduce the scale down whilst still incorporating the ADC.

[RodgerDodger008]

That's quite an increase in focal ratio (27%) - and accounts perfectly for the need to increase either the gain or the exposure to keep the histogram the same as when not using an ADC as you're now spreading the light out over that many more pixels.

Difficult as it may be to physically (and psychologically) achieve, I'm with Darryl on the smaller focal ratios. The vast majority of the time, imaging at somewhat less than the apocryphal "5x pixel size" will yield better-looking results.

Makes sense on many levels, need to experiment a bit to get this right. 🤔