Have you ever had a doh! moment?!

[dannybgoode]

For some time I've been trying to sort a way to getting a fine focuser on my TMB 105/650 without modify the rather lovely stock one as whilst it works well it's not precise enough for AP or very high magnification EP's.

A while back I was rather pleased with myself for figuring out that my Moonlite SCT unit would accept a threaded nose piece from a 2" extension tube. Job jobbed I thought until I tried it and with the tube that screws onto the ota to hold a 2" ep I could not get enough inward focus. I was a bit disappointed to say the least.

Today, having read an old S&T article on my scope I realised something. The tube unscrews to remove a 100mm extension 🤣.

As it happens this is brilliant news as I have an autofocus unit on the way and now it'll be a very quick job to swap the Moonlite between my TMB and Meade SCT and have autofocus capabilities on both...

[Xilman]

All too frequently. 8-(

My Doh! moment related to focusing was when I realized that I could make a Bahtinov mask out of a sheet of corrugated cardboard. Printed out a full-scale design onto 12 sheets of A4 paper (this for a 0.4m scope), glued them to part of the packaging in which a replacement kitchen oven was delivered a couple of weeks earlier, then attacked it (very carefully!) with a Stanley knife and a steel ruler.

Works a treat, after two years or so of focusing by guesswork I now get perfect focus very quickly. Bahtinov masks at this aperture do not seem to be available and extrapolation from what is on sale had led me to suspect that a custom product would be serious dosh.

I confess that I never thought I would rule an optical-wavelength diffraction grating with a craft knife.

[andrew s]

22 minutes ago, Xilman said:

All too frequently. 8-(

My Doh! moment related to focusing was when I realized that I could make a Bahtinov mask out of a sheet of corrugated cardboard. Printed out a full-scale design onto 12 sheets of A4 paper (this for a 0.4m scope), glued them to part of the packaging in which a replacement kitchen oven was delivered a couple of weeks earlier, then attacked it (very carefully!) with a Stanley knife and a steel ruler.

Works a treat, after two years or so of focusing by guesswork I now get perfect focus very quickly. Bahtinov masks at this aperture do not seem to be available and extrapolation from what is on sale had led me to suspect that a custom product would be serious dosh.

I confess that I never thought I would rule an optical-wavelength diffraction grating with a craft knife.

Your next Doh! Maybe forgetting to remove it 😏.

Mine are so frequent they form a peicewise differentiable world line.

Regards Andrew 

Edited March 5, 2021 by andrew s

[Xilman]

3 minutes ago, andrew s said:

Your next Doh! Maybe forgetting to remove it 😏.

Been there, done that.

[Starwatcher2001]

I spent a few hours trying to persuade my new SkySense system to work before throwing it to one side and going manual. When I packed up for the night I realised I'd left the lens cap on. It's no longer black.

[Chefgage]

I have read a few posts about people leaving lens/scope caps on and every time I have thought that seems a bit daft, not something that I would ever do. Cue me one night spending 10 minutes wondering why I could not see anything in the LCD display of my DSLR. Stars on the LCD display are always quite dim and few and far between but this was ridiculous.  Hmmm let me just look at the end of the scope, maybe it's dewed up. Nope scope cap is on. Just a little bit of quiet swearing and then on with the imaging!

[dannybgoode]

And no, I have never tried to plate solve or guide off an out of focus camera where the 'stars' are hot pixels or dust. Never ever...

[The Lazy Astronomer]

Spent about 30 minutes imaging before realising l hadn't focused. 

Another time I spent about 10 minutes trying to work out why my mount wouldn't connect to the laptop... helpful hint: much easier with usb cables plugged in.