Alien 13

I used to set up and image from my garden with my dog and cat in attendance and felt perfectly safe...

Alan

The only way I know of changing this sort of thing is by changing the screen resolution...

Alan

As a rough guide the Canon 1100D works best with an ISO of 800 or 1600, the exposure time will depend on a few factors but the histogram readout that is available on the camera will tell you if you need to increase the time or reduce it, aim for a main histogram peak around 1/3 the way from the left hand side. Most DSLR cameras seem to work better in terms of noise with max exposures no longer than 2-3 minutes, also allow a cool down time (10-20 seconds) between shots.

Alan

The later Canon cameras in the mid range like the 650/700/750D can suffer banding issues due to the use of their hybrid pixel AF which was introduced to give better AF performance with video shooting.

The slightly older 600D is fine though as are the 60/70/80D models, you might get hold of a used 60D or 70D within your budget so worth looking around at places like MPB and Wex.

Alan

I have never been a fan of Bat masks (hate them) when used with a DSLR, the liveview screen on camera (not a PC) will tell you all you need to know about focus.

Alan

9 minutes ago, vlaiv said:

Good question. I know that SCTs have issue with spherical correction and back focus, or rather there is spherical aberration if you focus far away from "ideal" focus point. Not sure if it applies to MCTs as well.

Another important point is if focus position is optimized for stock 1.25" diagonal and whether you should calculate things from that point.

I actually bought an SCT to T adapter by mistake thinking it might fit a year ago and have noticed it is a good 50mm longer than the original so that would put the focus point at a similar position to that if you used a diagonal. I guess the Mak might also be optimized for a certain focus point but not realy tried any comparison tests.

Alan

I do have another question regarding alternative visual backs, the Mak has a huge range of back-focus so is it better to use a short adapter meaning the main mirror is further down the tube or a much longer one that puts the sensor position at a similar point to that obtained if you were using a diagonal and eyepiece?

Alan

Thanks folks, looks like it is 45.4mm and as far as I know from looking online its the same for all the small Maks up to the 127mm.

The reason I am looking for a swap is that the internal diameter of the original is 1.25 inch and is fairly long so wondered if it contributed to vignetting with a DSLR fitted....

I cant think why they chose such a daft size on these instruments?

Alan

I am looking to replace the visual back on my C90 with something of better quality, there is no requirement for eyepiece fitting so a straight ?????? to T thread would be ideal.  The problem is that I cant find any info on the thread size of the original and there seems to be a number of different sizes depending on the age of the scope (mine is a new one), a quick measurement across the threads reads a 45.4mm. Has anyone got any thoughts?

Alan

My biggest problem is finding cases for my projects, the audio ones especially as I like them to be machined out of  a block of aluminium... the extruded cases are a reasonable second best for some less critical builds.

Alan

When we used to make in house test equipment the front panel was printed onto self adhesive white plastic sheets (cant remember the name but it was tough material) then stuck onto aluminium, this formed not only the identifiers for switches etc but a drilling template.

Alan

P.S. I think it was these http://www.simpsondonald.co.uk/downloads/identification/rmkA4.pdf

I have never been bothered by exit pupil size, my best ever views have been with military spotting scopes with EPs over 15mm.

Alan

Brilliant, that moment where the Moon passes the earth is surreal...

Alan

It will hit either the Earth or the Moon but the results will be similar..

Alan

15 minutes ago, Adreneline said:

This is a fairly ridiculus shot of the Pacman taken after I calibrated the filter wheel - not an ideal choice of lens for this target but useful for testing the tracking and imaging train I guess. There is only minimal edge cropping to the image. This is 12 x 120s of Ha, OIII and SII - all without guiding.

Thanks again for your help and the critical assessment of my images - much appreciated.

Adrian

Thats a cracking shot, I like lots of space around an image, far too many crop the life out of a good composition.

Alan

I would love a printer that could produce Bakelite parts, odd that the very first "plastic" is still the best 

Alan

3 hours ago, Ruud said:

I am saving for a new light bulb.

Me too, I need a second LIFX bulb, not cheap......

Alan

I think this one has our name on it, eastern Europe is my prediction but its a planet killer so dont matter.................

Alan

Whats wrong with imaging the Moon, its by far the best target out there.....................................................

Alan

1 minute ago, wimvb said:

3500 for a laptop? That must be some beast. 

It is, my last one cost £2200 nearly 4 years ago and still going strong but just starting to get a bit leggy so will need an upgrade in a couple of years time.

Alan

Saving for new laptop, only £3500 to go......

Alan

I quite fancy a monocle and a pair of trousers where the waist comes up to my armpits, would also like a bowler hat to top things off.

Alan

The 600D needs an ISO of 800 or 1600, as to focusing use the flip out screen and get rough focus on a bright star then use the zoom X10 to finalize focus by getting a very dim star to blink on/off with the slightest movement of the focus ring.................during focusing set the ISO high and shutter to 20 seconds (not bulb) then change them back for shooting. Another thing is dont use the camera tethered to a larger screen for focusing, the camera screen is much much much better.

Alan

12 minutes ago, Uranium235 said:

Behold... it's a miracle!! Three weeks this took (plus a load of chasing emails) 

But it's now "game on" 

I am sure you had 1...................................2.....................................or maybe 3 before, I would never let mine go 

Alan

It all depends on the focal length of the lens/scope, a 50 mm lens for example could go for hours..

Alan