Jump to content

Canada's top-tier Telescopes & Accessories
Be as specific as possible when reporting issues and *ALWAYS* include the full version number of the application you are using and your exact *CAMERA MODEL*
NEVER POST YOUR KEY IN ANY PUBLIC FORUM, INCLUDING THE O'TELESCOPE SUPPORT FORUM ::: IF YOU DO YOUR KEY WILL BE DEACTIVATED WITHOUT NOTICE!
  • 0

Taking Flats in Current Version of BYE


rockstarbill
 Share

Question

Hey all,

 

Looking for some up-to-date guidance on taking flats in BYE. I read through the older threads on this, and it seems that using AV-Flat is the setting I want. There was some discussion about the histogram using the JPEG image and not the RAW, has that been resolved? If not, what is the best way to take good usable flats in BYE? I am on the trial right now, and this is an issue that could be a deal breaker for purchase. I could always look at the stats in Nebulosity (or just take the flats there) or PixInsight, but that kind of defeats the purpose IMHO.

 

Camera is a Hutech 6D, in case that matters...

 

Clear Skies,

Bill

Link to comment
Share on other sites

12 answers to this question

Recommended Posts

  • 0

No worries...

 

TV means Time Value... it's a shutter speed.  You have Bulb, TV up to 30 seconds, and AV which lets the camera decides the TV exposure duration.

 

AV-Flat = camera decides the TV exposure duration.

TV = you decide so you can increase the duration.

 

Hope this helps,

 

Regards,

Link to comment
Share on other sites

  • 0

Use a TV value instead of AV-Flat; that gives you more control.  Push this histogram until it is about 2/3 in from the right.  That should do it.

 

Yes, the histogram is still using the embedded jpg.  If you feel you need to expose more increase the TV duration until the histogram is to the far right but make sure the hump is still withing the grid area.

 

Regards,

Link to comment
Share on other sites

  • 0

Use a TV value instead of AV-Flat; that gives you more control.  Push this histogram until it is about 2/3 in from the right.  That should do it.

 

Yes, the histogram is still using the embedded jpg.  If you feel you need to expose more increase the TV duration until the histogram is to the far right but make sure the hump is still withing the grid area.

 

Regards,

 

Sorry for my ignorance, but what do you mean by TV value? :) 

 

Thanks for responding, I enjoyed the 2 hour long video you posted. That is quite informative! 

Link to comment
Share on other sites

  • 0

No worries...

 

TV means Time Value... it's a shutter speed.  You have Bulb, TV up to 30 seconds, and AV which lets the camera decides the TV exposure duration.

 

AV-Flat = camera decides the TV exposure duration.

TV = you decide so you can increase the duration.

 

Hope this helps,

 

Regards,

 

Thanks! That should do the trick then! 

Link to comment
Share on other sites

  • 0

Tv means "shutter priority". When shooting with a lens, you set the exposure time and the camera adjusts the aperture (f/stop) to achieve the correct exposure.

 

The Av Flat shooting mode lets the camera's exposure meter decide the exposure for you.  It may be useful, especially if you are using a constant, artificial light source, to get an initial exposure.  Then you could change to manual mode and tweak that exposure to get the right histogram for your flat frames.

 

Tv means "shutter priority", as opposed to Av which means "aperture priority". What Guylain is saying is that you should adjust the exposure duration yourself to get the correct histogram for your flat frames.

 

Also, your stacking software will dictate the requirements of the flat images, but typically you should use the same image type (Raw or Jpeg) as your lights. I strongly recommend shooting only RAW for all image types. But would especially recommend not trying to mix JPG flats with RAW lights, even if your stacking software allows it, which it probably won't.

Link to comment
Share on other sites

  • 0

Tv means "shutter priority". When shooting with a lens, you set the exposure time and the camera adjusts the aperture (f/stop) to achieve the correct exposure.

 

The Av Flat shooting mode lets the camera's exposure meter decide the exposure for you.  It may be useful, especially if you are using a constant, artificial light source, to get an initial exposure.  Then you could change to manual mode and tweak that exposure to get the right histogram for your flat frames.

 

Tv means "shutter priority", as opposed to Av which means "aperture priority". What Guylain is saying is that you should adjust the exposure duration yourself to get the correct histogram for your flat frames.

 

Also, your stacking software will dictate the requirements of the flat images, but typically you should use the same image type (Raw or Jpeg) as your lights. I strongly recommend shooting only RAW for all image types. But would especially recommend not trying to mix JPG flats with RAW lights, even if your stacking software allows it, which it probably won't.

 

I use PixInsight and I only shoot in RAW mode. Once the skies clear up I will give this a go and see how it does. I use T-Shirt flats.

Link to comment
Share on other sites

  • 0

Also, realize that the "Rule of Thumb" about Flats needing to be of a specific ADU Range are rather Outdated.  That Rule was developed at a time when most of the Sensors were Early / Low-priced CCDs which had significant Linearity Issues.  These days, all DSLRs and most CCDs have Very Wide Linear Regions.  So, the reliance on Near-Exact Histogram Placement is not as Critical.

Link to comment
Share on other sites

  • 0

Use a TV value instead of AV-Flat; that gives you more control.  Push this histogram until it is about 2/3 in from the right.  That should do it.

 

Yes, the histogram is still using the embedded jpg.  If you feel you need to expose more increase the TV duration until the histogram is to the far right but make sure the hump is still withing the grid area.

 

Regards,

I see that Bulb, Tv and Av are all mentioned several times. I cannot find Tv anywhere.

Is there a tutorial on how to use Tv?

Rich

Link to comment
Share on other sites

  • 0

Rich,

 

Tv is a photographic term that stands for Time Value. In normal terrestrial photography it is a shooting mode where the shutter speed is fixed by the photographer and the aperture (f-stop) is altered by the camera's processor to give a correct exposure. Of course, this only makes sense when using a lens that supports a range of f-stops. When the camera is connected to a telescope, the aperture is fixed.

 

Tv mode is different from BULB mode, although both modes fix the exposure duration in advance of shooting. In BULB mode the shutter is controlled externally from the camera; like with a remote shutter, interval timer, or computer. BULB mode is typically used to provide exposures longer than 30 seconds, as is common for astrophotography.

 

When Guylain says to "use a TV value" what he is saying is to choose a numeric shutter value (not BULB, AV-Flat, or Program) from the Shutter dropdown list in BYE's Capture Plan Center. That shutter value would be somewhere between 30 seconds down to 1/4000th of a second (or shorter, if your camera supports it).

 

When BYE shoots a 2 minute BULB exposure, it issues a command to open the shutter and 2 minutes later it issues a command to close the shutter. When taking a 1/2 second Tv exposure, BYE tells the camera to take the 1/2 second exposure and the camera controls the opening and closing of the shutter.

 

For shooting flat frames you would take a series of pictures while varying the shutter value to shift the image's histogram so that the left-to-right position of the peak of the hump is slightly above the middle. The longer the exposure the brighter the image and the further to the right the histogram peak should be.

 

I hope this helps.

Link to comment
Share on other sites

  • 0

Rich,

 

Tv is a photographic term that stands for Time Value. In normal terrestrial photography it is a shooting mode where the shutter speed is fixed by the photographer and the aperture (f-stop) is altered by the camera's processor to give a correct exposure. Of course, this only makes sense when using a lens that supports a range of f-stops. When the camera is connected to a telescope, the aperture is fixed.

 

Tv mode is different from BULB mode, although both modes fix the exposure duration in advance of shooting. In BULB mode the shutter is controlled externally from the camera; like with a remote shutter, interval timer, or computer. BULB mode is typically used to provide exposures longer than 30 seconds, as is common for astrophotography.

 

When Guylain says to "use a TV value" what he is saying is to choose a numeric shutter value (not BULB, AV-Flat, or Program) from the Shutter dropdown list in BYE's Capture Plan Center. That shutter value would be somewhere between 30 seconds down to 1/4000th of a second (or shorter, if your camera supports it).

 

When BYE shoots a 2 minute BULB exposure, it issues a command to open the shutter and 2 minutes later it issues a command to close the shutter. When taking a 1/2 second Tv exposure, BYE tells the camera to take the 1/2 second exposure and the camera controls the opening and closing of the shutter.

 

For shooting flat frames you would take a series of pictures while varying the shutter value to shift the image's histogram so that the left-to-right position of the peak of the hump is slightly above the middle. The longer the exposure the brighter the image and the further to the right the histogram peak should be.

 

I hope this helps.

Hi Rick.

Thanks so much, that is a great explanation. It is working fine.

Rich

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

This site uses cookies to offer your a better browsing experience. You can adjust your cookie settings. By closing this banner, scrolling this page, clicking a link or continuing to browse otherwise, you agree to the use of cookies, our Privacy Policy, and our Terms of Use