ASTROPHOTOGRAPHY - TIPS Last updated: 28 August 2005

This page documents astrophotography comments, tips, and photos. Contributions welcome. Be certain to see the other articles on the main Astrophotography page.

Subject:	ETX 125 guided astro-photo at prime focus
Sent:	Friday, August 26, 2005 23:44:37
From:	Fernando Campuzano (fcamp@ya.com)
I've recently purchased a digital SLR camera and would like to use it
with ETX 125 at prime focus. Instead of Meade 64 T-adapter, I'm
unsuccesfully seeking for an off-axis guider similar to Meade #777 for
the LX-series, but for the ETX. I've heard about an adapter for the ETX
to match accesories for the LX (a Scopetronix model) but didn't find it
in any Internet site with shipping in Europe.

Could you help me? Do you know some other alternative? or, a good
Internet site with shipping in Europe?

Thanks in advance

Fernando
Guadalajara, Spain

Subject:	City astronomy
Sent:	Tuesday, August 16, 2005 09:01:56
From:	Mike Lewis (mikel137@eskimo.com)
Your website is valuable.  I used it when first setting up to do
astrophotography. I'd like to share a photo with you.  My small downtown
Seattle apartment has only one northern window and the view is about 60d
altitude and 30d azimuth.  Astrophotography is rewarding, though and a
great deal of fun.  This photo came out fairly well.  The problem of
getting rid of glare is the worst.  PhotoImpact's Tone Map is excellent
for eliminating background noise (and most faint stars) but keeps some
visible. I used to go up to Table Mountain or other places but the
hassle of setting up for only one or two night's work is awful -- home
limits the sky but the elaborate events that need to take place can be
in a stable place.

JPG's of both the original and the adjusted images are shown.  The
original was an 11Mb 2272x1768 TIF file.  It is not mentioned in the
photo that, besides Tone and Gamma adjustments, an unsharp mask was used
on the three RGB channels.  Next time, the CMYK channels as well.  
Adjusting gamma on the CMYK images is iffy, there is no good measure and
these images are all much different.






Michael Lewis
Seattle

Postscript:  Forgot to mention the photo of Errai was one eight-second
exposure at f:2.6.

Subject:	Question about dual axis drives for astrophotography -not spamm
Sent:	Thursday, August 11, 2005 18:58:52
From:	John Dooley (j1dooley@bop.gov)
Sure like the cool site on the Oracle Observatory, and good luck with
any pictures of the meteor storm tonight!!! Mike,

I've been toying with ideas for a decent dual axis motorized mount since
I picked up a Canon 20D (unfortunately not the 20Da model!!!) and after
a fair search have only been able to come up with sellers for these in
Canada, UK and Australia. Do you know of anyone who has utilized them
for astrophtography and/or a source for one in the 100-200 dollar
range??? I have my ETX125ec with a Scopetronix piggy back mount, but
dont really have a good enough system set up to transport my scope out
to favorable areas and also have not yet invested in a better tripod to
support polar alignments. - I did get smart after purchasing my scope a
few years ago and sent it directly to Dr. Clay for the Supercharge.
Still wish I could have taken advantage of the eyepiece deal when it was
so popular, alas!!! poor timing. Anyways, fine business on your Nikon
and always looking for news of your travels back from Arizona. Good job
packing that little car Mike!!! Wheres the iPod????

John Dooley
Victorville, CA

Subject:	etx focal reducer, eyepiece port
Sent:	Wednesday, August 10, 2005 14:15:40
From:	A. Sidney Johnston (ASJ@c-m.com)
I have been searching vendor pages for a focal reducer for my ETX 125,
where the focal reducer fits into the eyepiece port.

I want to use the Meade Deep Sky IMager with a wider filed of view,
which the focal reducer shuld provide.

Meade has two models, a 2x and a 3x, both advertised as "reducer
correctors", which screw onto the back of the telescope, and then hit
the fork base if one goes to high DEC.

Do you know of any vendor who sells a focal reducer, preferably a
reducer corrector, which fits into the ETX eyepiece??
 
Thanks
Sid Johnston

And:

Thanks for your prompt reply.  I had seen your write up about the Shutan
wide field adapter.  However, I wondered why it is necessary to buy a
prism when all that is needed is an in-line device to converge the rays.

Perhaps the range of focusing of the ETX is not great enough to properly
place the prime focus behind a converging lens of the focal reducer,
when the focal reducer is placed in the eyepiece port.

Do you think that a design limitation may be why Meade has two models of
focal reducer for the in-line rear port, but none for the eyepiece port
of the ETX??

Thanks
Sid

And:

I just ordered a focal reducer which screws into the filter threads of
either a ccd camera or an eyepiece.

I ordered from the link http://webcaddy.com.au/astro/adapter.htm, and I
ordered both the lens and the extender tube.

If you are interested, I will let you know how it works.

Sid Johnston

Subject:	Stacked image Anomaly 
Sent:	Wednesday, August 10, 2005 02:42:27
From:	C.A.Warburton (C.A.Warburton@lboro.ac.uk)
My most recent and best shots of Jupiter ( the AVI's were taken a couple
of months ago ) seem to exibit striations accross the image. The Avi's
were stacked in Registax and whichever version I use seems to produce
the same effect. This unfortunately limits the amount of enhancement I
can use as the lines accross the image are enhanced as well.

Do you know if any one else has had this problem and if so is there a
way of fixing this?

I've attached a slightly over enhanced image as an example.





Many thanks Mike,
Kind regards,
Chris Warburton,
Derbyshire U.K. 

Subject:	Removing "hot pixels"
Sent:	Saturday, July 30, 2005 23:26:54
From:	Tom and Lori (lortom7@earthlink.net)
I found a great free program that removed the "Hot Pixels" on your dark
digital photography photos.  This works well.  The name of the program
is HotPixels.

There is also a great filter simulator that simulates different Wratten
filters.

Here are the links:
 
http://www.mediachance.com/digicam/hotpixels.htm
 
http://www.mediachance.com/digicam/filtersim.htm
 
Clear skies,
 
Tom

Subject:	learning to scale images questions
Sent:	Saturday, July 23, 2005 20:54:02
From:	Steve Dang (stevedang@gmail.com)
Im trying to learn how to scale my images and I have a couple of
questions about reducers.  Wondering whether you could help me.

Attached is a picture of the moon , features of crater plato and vallis
alpes. I used a Moggs .63 reducer at 50 mm from the CCD at prime focal
on etx 105 ec. Tested the reducer on jupiter and measured the diameter
at 31 pixels. Without the reducer jupiter measured 49 pixels arcross. 
so around .63 x reduction factor.  So im fairly confident at this stage
that it works at a distance of 50 mm.

The etx 105 is at F14 so 14 *.63 = F8.8

Getting the focal length :

8.8 * 105 ( for the diameter of the scope) = 926.1 mm.

From http://ccdastrophotography.com/CCDfov.html
using a meade dsi.  9.6 microns x 7.4 mins.

Somehow i get 4.89 mm X 3.690 mm for the dimensions of the ccd chip. :)
w ArcMin = (4.896 x 3438) / 926.1 = 18.17562682215arc mins
h ArcMin = (3.690 x 3438) / 926.1  = 13.6985422740 arc mins

So  get 18.17 arc mins X 13.69 arc mins of sky.

Diameter of the moon is 
 3476 km .

moon is 31.38 arc mins around on that day.

thus (18.1756268/ 31.38) * 3476

2013.3358455646 kms x axis 

my ccd is 510 pixels wide thus
2013.3358455646/ 510  kms = 
3.9477173442 kms per pixel

so Crater plato at 27.66 pixels =~109.1938617 kms diameter.

That all seems all  nice and fine but I ve increased the distance from
the CCD to the focal reducer and the CCD unit closer to the scope so it
would focus properly.

Increased it from 50 mm to 60 mm.

When compare the new images i get a reduction factor of .28

That would bring down my scope to a F4. instead of F8. just by moving it
further by 10 mm?

http://legault.club.fr/index.html 
Describes the formula for focal reducers. so for my etx 
Distance= 50 mm
Reduction factor = .6 

therefor FR = D/(1-R) = 50 / (1 - .63) = 135 mm focal length of reducer.

I was wondering if its possible to transpose this r = 1-(D/fr) because
im unsure how to find the focal length of the reducer?  When i check it
by eye the focal length appears more like 200 mm.  And when i use 200 mm
in :

d = Fr*(1-R) 
D = 200*(1-.63) = 74mm as the nominal distance to which the reducers
works at .63.

But at 50 mm i had the same reduction factor?

I dont know how to work out the focal length of the reducer to find the
focal ratio to ultimately get the fov.

hope some of it makes sense.

And:

Sorry Mike :)
Thats fine.  Ive found a great site that discusses reducers etc and Ive
found my answer :).

from here :

home.earthlink.net/~celstark/id7.html

I bet if i looked in your site i would have found the same link somewhere.

I didnt know some basic information on astronomy so this site was good
for me.
http://www.astronomyforbeginners.com/astronomy/howknow.php#masssun

Thanks for replying and i Hope next time I would have some nice pics of
galaxies from the southern hemisphere.
Melbourne. Australia.

Subject:	Re: MaxView DSLR II
Sent:	Thursday, July 21, 2005 11:30:23
From:	Paul Giguere (pgiguere@earthlink.net)
The Scopetronix

MaxView DSLR II looks great (nice write-up) but do you think that it
would be too heavy when used with a Canon 10D on my ETX105PE?

Paul Giguere

Subject:	Re: Piggyback astrophotography on ETX105PE?
Sent:	Thursday, July 21, 2005 07:59:10
From:	Paul Giguere (pgiguere@earthlink.net)
I was wondering if anyone has tried piggyback astrophotography using an
ETX 105PE? I'm thinking of getting the Scopetronix mount but it seems to
me like the LNT might get in the way of properly mounting the adapter.
It seems like the mount may not come down close enough to the forks.

Paul Giguere

Subject:	Focusing a Faint object
Sent:	Tuesday, July 19, 2005 01:41:25
From:	Mat Little (elicitbmx@insightbb.com)
After toying around with my new ETX-125PE, i decided to try a polar
align, to my suprise it work pretty well for the first try. I saw
polaris in my eyepiece, and when asking autostar to go to the andromeda
galaxy, it found it, and almost had it dead center.

Having purchased the t-mount for my Canon Digital Rebel, I decided to
give it a test spin. I pointed the scope at mars, and got it centered in
the eyepiece. I then switched the mira so that i could see throw my
camera eyepiece. This resualted in mars being a large ring, so i focused
it pretty well, with out a problem. ( i have read the article on the
hartmann mask, and it seems like a good idea when focusing bright
clearish objects)

Problem came when i pointed back at the Andromeda Galaxy. leaving the
scope alone for about 5 minutes, and checking periodicly, i could see
that it was tracking well, and that the galaxy stay center. So i
switched the mira, and laid on the ground so i could get to my cameras
eyepiece. What did i see? nothing, not enough light to see rings of a
possible star. So i turned the focus knob in, like i did with mars to
try and see if something could come into focus. Nothing. Any usefull
tips could really help, thanks.

-Mat Little

(and if it helps, im on a very tight budget seeing that i just droped
1k$ on this wounderful telescope)

Subject:	Why Polar Alignment for Photography?
Sent:	Friday, July 15, 2005 07:27:04
From:	Brett Yesukaitis (byesukaitis@hotmail.com)
First, I want to thank you for the wealth of information that you and
your site provide.  It has helped me embrace this new hobby instead of
packing it up.

I've been working with my ETX-70AT for 7 months now (a Christmas gift),
and am starting to look into astrophotography.  Considering the
limitations of the scope and cost involved, I thought I'd start with the
piggyback method.  What I am trying to understand is why Polar Alignment
is required?  One of the selling points of the ETX (and many other Meade
models) is the tracking feature.  If it indeed tracks the target
accurately (within reason), why the special mounting..especially with
the Piggyback method?

Just curios.  Any information or direction is appreciated.  Again,
thanks for a great site.

Brett

Subject:	ETX-125PE
Sent:	Wednesday, July 13, 2005 09:35:23
From:	User721401@aol.com (User721401@aol.com)
Just wondering if it is possible to photograph the shuttle and ISS when
they are docked using the ETX125-PE and the Nikon D70.

If it is possible,  what suggestions would you have to obtain such a
picture.

Thanks
Dan

Subject:	Etx 125/ digital camera photography
Sent:	Tuesday, July 12, 2005 18:44:29
From:	al moro (ynos900@yahoo.com)
Recently I bought myself a digital camera, the picture that I sent you.
I usually hold the lens above the eye piece, but I find that it is
difficult because that light seems to come in a angle instead of the
full center, when I am trying to take a picture of the moon.

I was wondering how I can improve my pictures by using what different
type of eye piece. The eye piece that I am using is the standard 26mm
that comes with the ETX 125.

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