Full disc H-alpha 16 & 17 August 2023

[Dave Smith]

Seeing some lovely images on here using a 178MM made me look into choosing the right camera for a scope and concluded that with my 80mm Lunt that I would benefit using the smaller pixels of the 178 for full disc images.

There is one snag. My 174 will run at 110 frames per second whereas the 178 only does around 18 per second. For a clear sky that is not a problem but when chasing gaps in the clouds it is a different matter. Another snag is that I can only capture around 90% of the full disc and so two exposures are needed.

These two images are with a 178.

 

Dave

[Mandy D]

@Dave Smith Those are spectacular images.

[inFINNity Deck]

Hi Dave,

these are nice captures. You may be able to increase speed by enabling the HighSpeed option and/or by lowering the USB Traffic setting. Also capturing in 8bit mode (instead of 16bit) may be beneficial. I presume you use a square ROI?

Which scope did you use (and is that a double stack?)?

Nicolàs

 

[Dave Smith]

Thank you Nicholas. I did try a square ROI but it made little difference. I don't know how to do the the other two.

My scope is a single  stacked 80 mm Lunt. 

Dave 

[symmetal]

The tips by Nicolàs are useful, though I think he meant to say try raising the USB traffic setting. 🙂 I use Firecapture and you can access these settings by clicking on the 'More' button in the Control section. I manage 40fps full frame with my ASI178 at high speed enabled and 30fps if disabled. At USB traffic minimum (40%) I only get 11fps and I find it's fine at 100% where I get the 40fps. For large format cameras you can get missing images or errors at 100% but it's fine with smaller sensors.

Also disable gamma when capturing, or set it at 50 which is the same thing. Gamma processing takes a lot of processor time so drops your frame rate.

 

Alan

[Dave Smith]

Thank you Alan. Very helpful. Next time out I will give it a try.

Dave

[symmetal]

Also, concerning using a ROI, it's only reducing the ROI height that will improve your frame rate. ROI width has no effect on the frame rate as the sensor is read out line by line and ROI line cropping is done afterwards. As you have to do a 2 panel mosaic, reduce the ROI height as much as you can while leaving a reasonable overlap.

I have gamma set to minimum (1) when focusing as it improves the image contract, but always remember to turn it off before capturing.

I have a 60mm Lunt, and luckily the Sun just fits on full frame with the ASI178. 😊

Alan

Edited August 18, 2023 by symmetal

[Dave Smith]

Thank you. That is interesting. In that way there is plenty of room to crop and have a decent overlap.

Dave

[JeremyS]

My goodness Dave, you really are on a roll! Spectacular 👍🏻👍🏻👍🏻

[inFINNity Deck]

2 hours ago, symmetal said:

The tips by Nicolàs are useful, though I think he meant to say try raising the USB traffic setting. 🙂

Well, I actually meant lowering the USB traffic to 0 or 1:

As can be seen a 0 setting results in a 23FPS for my QHY163 mono at 3500 x 3500 pixels (I use it with my LS80THA single stack). It is not much faster than Dave is getting, but much better than 1.7FPS when USB traffic is set to max.

But perhaps this differs for the ZWO camera?

Nicolàs

 

[symmetal]

5 hours ago, inFINNity Deck said:

But perhaps this differs for the ZWO camera?

Interesting. It looks like the QHY has the meaning of the USB Traffic slider reversed, compared to the ZWO. QHY 0 is Zwo 40% and QHY 60 is Zwo 100%. The Zwo figure represents what percentage of the available USB bandwidth can be used by the camera. 🙂

Also @Dave Smith, I forgot to say that they are excellent images.🤗

While reducing the ROI width won't affect the camera fps, it will give a smaller file size, so if you have a bottleneck in writing to disk, then reducing the ROI width can help you maintain the camera fps. If you have an SSD for storage, then this won't be an issue. 🙂

Alan

Edited August 19, 2023 by symmetal

[Dave Smith]

Thanks Alan. I do  have an SSD.

Dave

[inFINNity Deck]

14 hours ago, symmetal said:

Interesting. It looks like the QHY has the meaning of the USB Traffic slider reversed, compared to the ZWO. QHY 0 is Zwo 40% and QHY 60 is Zwo 100%. The Zwo figure represents what percentage of the available USB bandwidth can be used by the camera. 🙂

Indeed the ZWO cameras work the other way around, here a test with a ZWO ASI1600MM Pro Cool at 3200 x 3200 pixels ROI (same imaging-chip as the QHY163 mono):

Also the figures differ: minimum is 40, maximum 100 (vs. min 0 and max 60 for the QHY).

Nicolàs

 

[Dave Smith]

Thank you both very much. I now seem to get between 80 and 90 frames per sec having changed the USB traffic and a crop. That is perfectly acceptable to me.

By the way, I have been away for just over a week and have just tried the new settings.

Even with full frame I am getting ~60 f/s

Dave

[symmetal]

2 hours ago, Dave Smith said:

Thank you both very much. I now seem to get between 80 and 90 frames per sec having changed the USB traffic and a crop. That is perfectly acceptable to me.

By the way, I have been away for just over a week and have just tried the new settings.

Even with full frame I am getting ~60 f/s

Dave

That's looking much better. 😁

Alan