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<DIV>Hi Mike,</DIV>
<DIV>By monochrome I mean black and white not colour. Imaging with no filter or
through a clear luminance filter is much the same thing. Usually the clear
luminance filter is put into the LRGB set to make all the filters par-focal,
therefore there’s no need to refocus when moving between the luminance sub
images and the RGB sub images. Having said that most luminance clear filters
contain an ultra violet and infrared blocking coating which is invisible to the
naked eye but will help sharpen the images if your telescope can’t focus the
wavelengths just outside the visible range.</DIV>
<DIV> </DIV>
<DIV>Higher end mounts sometimes do have the ability to track at custom rates in
RA and Dec which can be useful for following a very fast moving comet.
Using custom tracking rates will allow you to make exposures of a longer
duration than otherwise. Despite this and the fact my mount will track at custom
rates I still recommend you take a number of shorter duration exposures either
tracked at sidereal rate (or at a custom rate) and stack them together. Try
experimenting and decide for yourself.</DIV>
<DIV> </DIV>
<DIV>All the best</DIV>
<DIV>Peter</DIV>
<DIV> </DIV>
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<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=mikepaling@madasafish.com
href="mailto:mikepaling@madasafish.com">Mike Paling</A> </DIV>
<DIV><B>Sent:</B> Wednesday, May 02, 2018 7:08 PM</DIV>
<DIV><B>To:</B> <A title=comets-disc@lists.britastro.org
href="mailto:comets-disc@lists.britastro.org">BAA Comets discussion list</A>
</DIV>
<DIV><B>Subject:</B> Re: [BAA Comets] Help please?</DIV></DIV></DIV>
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<DIV>Hi Peter ...</DIV>
<DIV>Thanks for this .. I will try these ideas out when I get the next
opportunity.</DIV>
<DIV> </DIV>
<DIV>By “monochrome” do you mean using my L filter ... or is it no
filter???</DIV>
<DIV> </DIV>
<DIV>I forgot to say in my first message that my mount “allegedly” can track
comets as they move against the stars after I input the delta RA & Dec
values.</DIV>
<DIV> </DIV>
<DIV>Regards Mike</DIV>
<DIV> </DIV>
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<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=petercarson100@gmail.com
href="mailto:petercarson100@gmail.com">Peter Carson</A> </DIV>
<DIV><B>Sent:</B> Wednesday, May 02, 2018 6:56 PM</DIV>
<DIV><B>To:</B> <A title=comets-disc@lists.britastro.org
href="mailto:comets-disc@lists.britastro.org">BAA Comets discussion list</A>
</DIV>
<DIV><B>Subject:</B> Re: [BAA Comets] Help please?</DIV></DIV></DIV>
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<DIV>Hi Mike,</DIV>
<DIV>Welcome to the fascinating world of comet imaging. </DIV>
<DIV>Imaging comets is similar to deep sky object imaging except the target is
moving! Because comets move you’ll find an exposure longer than a minute or two
will smear out the comet. The actual longest exposure duration will of course
depend on how bright the comet is and how fast the comet is moving. What makes
comet observing fascinating is that all comets do different things including how
fast they move across the sky.</DIV>
<DIV>Your telescope at f/6 is well suited to comet imaging so I’d start off by
picking a moderately bright comet
<DIV
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take several consecutive exposures (say 10) of about 60 to 120 seconds duration
in monochrome only. Then stack the images with the comet as the reference point.
You’ll find the resulting image shows the comet fixed against a background of
trailed stars. This is the technique most comet imagers use.</DIV></DIV>
<DIV>
<DIV
style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>Have
a read of the BAA’s Comet section observing guide, section 5 deals with imaging.
<A title=https://www.britastro.org/node/6817
href="https://www.britastro.org/node/6817">https://www.britastro.org/node/6817</A>
When you mastered monochrome then LRGB colour imaging will be less difficult
because you’ll have an appreciation of the likely problem areas.</DIV></DIV>
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<DIV
style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>Good
luck</DIV></DIV>
<DIV>
<DIV
style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>Peter
Caron</DIV></DIV>
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<DIV
style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'><B>From:</B>
<A title=mikepaling@madasafish.com href="mailto:mikepaling@madasafish.com">Mike
Paling</A> </DIV>
<DIV style="FONT: 10pt tahoma">
<DIV style="BACKGROUND: #f5f5f5">
<DIV><B>Sent:</B> Wednesday, May 02, 2018 5:59 PM</DIV>
<DIV><B>To:</B> <A title=comets-disc@britastro.org
href="mailto:comets-disc@britastro.org">comets-disc@britastro.org</A> </DIV>
<DIV><B>Subject:</B> [BAA Comets] Help please?</DIV></DIV></DIV>
<DIV> </DIV></DIV>
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<DIV>Hi ...</DIV>
<DIV>I am trying to get into imaging comets .... I am very much a beginner with
this aspect of astro photography.</DIV>
<DIV> </DIV>
<DIV>I have a pretty decent permanent setup here in Nottinghamshire ... my mount
is capable of up to 20 minutes unguided tracking and my CCD mono camera has LRGB
(and also Ha) filters. My scope is a 123 mm x 780 mm focal length f6
refractor.</DIV>
<DIV> </DIV>
<DIV>Can anybody suggest suitable exposure times to use with my LRGB filters?
</DIV>
<DIV> </DIV>
<DIV>Many thanks in anticipation of any help that can be given to my question
:-)</DIV>
<DIV> </DIV>
<DIV>Regards Mike</DIV>
<DIV> </DIV>
<DIV> </DIV></DIV></DIV>
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