Switch10

9 hours ago, wimvb said:

For the initial stretch, I aim at a background value of about 10% (25), making sure not to clip any pixels, but in the final stretch, I usually lower this to about 6 - 8% (20) by using an S-curve stretch.

I follow the same workflow with linear stretching first followed by non linear but normally ended with pixel values of around 10 which just looked unnatural.

Good to hear a value of 20 (roughly) come up twice, that did look way better on my last image.  

Thanks - ive always winged it to some degree so that's helpful

Hi - I'm struggling to find the sweet spot for getting a consistent background value in my images that makes it look natural and not too dark (which to me looks over processed). Also if you put my images side by side the background sky values are always different so im after a consistent RGB pixel value to target.

Does anyone have a target pixel value range for the background sky rhat they aim for when tonal stretching L + RGB images and if so, what is it? Or do you do it what looks good image by image?

I recently processed M81 with a background sky RGB values of around 20-30 and it looked more natural than when ive had it around 10 on other images but wonder how others tackle this?

Thanks

Great image, exceptional clarity on the surface details.  Nice job.

Hi, this image was taken last night and is a composite of the best 600 frames of around 2100. Processed in registax and gimp to bring out sharpness and contrast. 

Shot through a f5 200mm reflector using an olympus camera.

Hope you enjoy! 

Thanks chaps - tried PA aligning last night rotating the RA axis so 0 was as the top (just so i was sure where to position Polaris) and it tracked nicely. 

That's not a bad shout. I do a similar thing with some masking tape on the dovetail to mark where I should lock in the OTA on the mount so i know it will be balanced.

1 hour ago, Aramcheck said:

The instructions on our EQ6 say to rotate the RA axis until 12 o'clock is at the top. To me this seems a bit crazy, given the cost of the mount & the risk in not getting the reticule rotation aligned perfectly.

Once the RA is rotated, I use the alt/az bolts to check the horizontal/vertical are aligned on the axis' as best I can, before positioning polaris at the required time on the clock face.

Cheers
Ivor

Thanks Ivor - will try that way next time I'm out. I agree it seems odd as to why they wouldn't just align the clockface reticule upright in the first place. It's an extra thing to fumble about in the dark with.

Hey everyone, i know this is a question that has probably been asked a million times but i need some help with it.

When my scope is in the home position with DEC axis at 0° and perpendicular to the RA axis, the clockface reticule in the polarscope is twisted clockwise 2 hours too far i.e. showing 12oclock where 2oclock would be on an upright clockface and 6 oclock where 8oclock would normally be. 

My question is where should i position polaris using its hour angle for my long/lat/time to get proper PA?

This is causing my grief as take this example- say i use my current clockface where 12 oclock is where 2oclock should be, if polaris hour angle was 8oclock say, I'd positon it at 8oclock on the clock face. If i rotated my RA axis so that 12oclock was at the 'top' and 6oclock at the 'bottom', that same alignment of 8oclock on the twisted reticule would mean polaris would be at 10oclock on the upright clockface - a difference of 2 hours.

Should i position polaris using an upright clockface (i.e. rotating my RA axis slightly so 12 is at the top) or position it on the wonky clockface where 12 is at 2? I have already calibrated my polarscope so that objects stay centre if you rotate the RA axis.

Hope someone can shed some light on this, thanks.

Welcome to SGL 😁

12 hours ago, wookie1965 said:

Have you considered one of these just fit like the front cover I had one for my 150p when I took pictures of the transit last time.

https://www.365astronomy.com/Solar-Filter-for-200mm-Newtonian-Telescopes.html

No i didn't know those were a thing, thanks for sharing! I'd seen metal cased solar filters but those were pushing the 100 quid mark.

Might consider getting one if the sun livens up and after my handmade filter undoubtedly falls apart.

Agree with the others for using the moon if you can as it's a bright, easy target. I then usually fine tune mine using a star like Vega to get it spot on. Have to do this each obseving session as i always end up knocking it when carrying it outside...

10 hours ago, wookie1965 said:

Is that a 150p or 200p

It's a 200pds but had to make the filter 6" as single a4 film didn't cover the opening and i didn't want to fork out another 20 quid for an extra sheet...

10 minutes ago, wookie1965 said:

Should get a blue Peter badge😁

A solid looking filter that. Mine looks okay from the front but was a dogs dinner at the back! It was safe at least 😂

38 minutes ago, wookie1965 said:

I bought Baader film and made a filter just for today.

Same here although today I learned my craft skills are woeful 😂

Frustratingly the sun is shining again here low in the south-west with only a few clouds but I've already packed the scope away and it was just too cold to stand out any longer (as much as I'd like a few more pics!).

Managed a few pics today before the clouds set in. This was the first transit I've observed so was really interesting!

Quick update. Managed a few hours outside tonight for the first time with my new SW 200PDS on the HEQ5.

Took a few attempts to align the mount using the 2 star alignment function but after a few tries, the tracking and slewing was spot on from the SynScan so not so worried now as I was initially in the original post. 

Couldn't check it against any DSOs though due to the gibbous moon lighting up most of the sky in my FOV but managed a few double stars and open clusters.

Thanks all for the advice.

Thanks Louise. All my inputs are spot on so will report back once I've tried the synscan out if the weather permits any time soon.

It just seemed odd that the coords where different. 

1 hour ago, Jiggy 67 said:

Can’t explain your issues but if it helps to put your mind at rest , I’ve recently been using a brand new SynScan, probably from the same batch as yours (with a 200PDS) and it’s bang on every time, appears to be far more accurate than my last one

Puts my mind at ease hearing that!

1 hour ago, Owmuchonomy said:

Short answer, no. Don’t bother with a polar scope it’s just a pain. Use the Polar Alignment routine in SynScan instead after doing a very rough North alignment. It’s much easier and I found it very accurate.

Doesn't the SynScan routine require you to use the polarscope? If not, could you explain how to do it?

This is my first GoTo mount so excuse all my questions 😁

25 minutes ago, Owmuchonomy said:

For visual purposes, the slight differences you describe will not affect the GoTo accuracy sufficiently to cause a problem.

Thanks for the reply Chris, good to know that impact will be minimal for visual use.

I'll be mounting a S/W 200P-DS on the HEQ-5 for astrophotography, will the coordinate differences have an impact there?  Assume the mount will be properly polar aligned to not complicate matters...

Hey everyone,

I received delivery of my HEQ-5 mount yesterday and have spent today putting it together and playing about with SynScan to get familiar with it while I wait for clear skies.

I've noticed that some of the data in the SynScan seems to be different compared to various apps i'm using, see two examples below taken from today. Note I've entered the correct time / long / lat / elevation info into the mount prior to these checks:

1. RA / Dec coordinates are marginally different to Stellarium so it will always slew to a slightly different position. An example is SynScan shows M31 as 00h43.7m RA, +41 24' DEC, while Stellarium shows it as 00h42.4m RA, +41 16' DEC. Not massively out but still out.
2. P.Scope position / Polaris HA are different to PolarFinder. An example is SynScan shows p.scope position as 10:06 and HA as 15h 48m. PolarFinder shows p.scope as 09:56 and HA as 16h 7m. Again not massively out but not the same.

My understanding is that RA/DEC coordinates for objects don't change (excluding obvious objects like planets etc) so why would they be different. My worry is that my mount will forever be skewing to slightly "off" coordinates.  I initially thought it may be because of the SynScan version being older but it is v4.39.04 and the latest on the website is v.4.39.5 so doesn't seem to be that.

I'm stumped, any ideas?

Quick update - i took everyone's advice and to future proof my investment, I just purchased a HEQ-5 mount and 200PDS scope. 

Here's hoping to clear skies soon 🤞🏼

1 hour ago, Raph-in-the-sky said:

Don't settle for possibly ok... Just buy the HEQ5 when you have the money

Thanks for the advice!