bomberbaz

On 28/10/2023 at 12:13, globular said:

I typically use the option in SkySafari to display my observation list on the map and then hop from one to the next nearest, rather than use the order they appear in the list.  This limits slewing - but I do miss some objects because they are gone before I get to that part of the sky.

How do you do this? I use SS6 for pretty much all my observing these days and often cram a bit too much on my lists so having them displayed on the map might help me be more organised and structured in my viewing whilst saving me printing off a list that often ends up sopping wet in dew.

Not actually into planetary imaging myself but though I would pop this up for those who are.

APM Telescopes. Atmospheric Dispersion Corrector (apm-telescopes.net)

Specs seem very good and I presumed it imaging related due to the 2 M42 fittings rather than 1.25" male/female.

I do think this is for the very serious people though as it is likely to push around £2K after import and vat costs. 🫢

56 minutes ago, Veloman said:

Hi, the scope is a WO Megrez 80 II, cradled in Skywatcher tube rings and mounted on a CG5 AS GT. The reason that I posed the question is because when I put set the tube rings on my surface plate & measured the machined heights there is a difference of 3 thou". I'm not able to accurately measure the screw hole's but they seem to be OK.

At the moment I'm the scope is being used for visual but I've treated myself to an ZWO ASI air plus and a ZWO ASI220 guide- camera with a view to starting imaging.

Many thanks for the replies.

Rob

Thanks for clarifying, it wasn't exactly clear. However both @StevieDvd & @900SL have answered in the manner I would have. Basically it's fine. 

Can you elaborate on what you mean please, what scope are you referring to and mount, plus is this for visual scope or imaging ?

got bins on standby but doubt thay will be needed

9 minutes ago, John said:

You have already had some good advice. All I will add is that I always try and finish on a couple of "easy" targets rather than something too challenging. That way I end a session in a positive frame of mind 🙂 

That is a rather obvious but brilliant piece of advice. Too often I have finished after an unsuccessful hit attempt at something difficult and thought, " what the hell, home time".  Better to  think, "wow, that was good, time to head back".

thumbs up!

yeh but tomorrow it's lunar eclipse day 🙄

alas I fear the weather gods will be conspiring against me on that night!

36 minutes ago, John said:

Yep. The largest I currently use is 5.25mm. I'm over 60 so I assume that my max dilated pupil has started to get smaller now.

24 minutes ago, globular said:

I'm around that too - 5.5mm last time I measured it.
So my f10.5 scope isn't too limiting as I get 5.4mm with my 56mm plossl - and, when the sky is nice and dark, DSOs pop with the right filters.
Personally I see no reason to go the reducer route for visual astronomy - just pick the right eyepiece.

Seems us older chaps adopt similar,  my biggest exit pupil are at 5.3 (age [cough] 60) as a future proof should see me good for circa 10 years.

But this wasted light discussion brings us back to my rationale for adopting a larger exit pupil in the opposite way, maximise your light grasp when needed (when using light limiting filters) on dimmer nebula dso. 

Just to help here it was I who suggested a reducer for increasing the exit pupil for use with narrowband filters in a different thread.

The op was looking at viewing the eagle nebula and was struggling to see it with no filter and a 25mm ep at 2.5mm exit pupil.

It was suggested by one commenter that a uhc filter would help but I chipped in with reducer for the larger exit pupil or a 40mm plossl as an additional measure to improve results.

My personal experience points to a 5mm exit pupil being optimum for line filters with 4-5mm being ok for the more forgiving uhc when used on diffuse nebula. I have read numerous articles in various forums and have yet to find anything to convince me otherwise.

So if you can live with the vignetting to have a strong response from a dim object at the centre of the eyepiece then it is still something to consider, a 40mm plossl is the other contender. 

@ONIKKINEN many thanks for this, I shall have a bash at this with what data I have and see what I come up with.

In the interim I found some excellent tutorials on YouTube by one guy who covers a broad range of subjects and goes through them with a Janet and John style for relative novice users to follow. My only problem is trying to remember them all🤣

20 hours ago, ONIKKINEN said:

For calibration, you can still use the stock script, or modify it a little bit. You can find the scripts in the scripts folder of your Siril installation folder, for my installation it is in C:\Program Files\SiriL and is probably for you too. The .SSF files can be opened and modified with word pad. The simplest way to modify is to just remove the lines at the end, like below:

Just remove those lines and the script ends with debayered and calibrated files with the prefix pp_light for each file. Move those files to another folder and then just delete all of the other files in the working directory. They are temporary files so nothing lost (just make sure you dont delete your actual raw data, keep it elsewhere) and then re-do the script with another dataset with its own calibration frames.

After calibrating any number of images from any number of nights, you will need to now stack manually. Its not too difficult to do, i think its just poorly explained (if at all) by Siril and is pretty confusing for someone using Siril for the first (or tenth) time. What you need to do is import all the files you want to stack into the "Conversion" tab. You dont have to worry about calibration anymore since you already calibrated all the data with the script before. Then in the "Registration" tab you will register (star align) the images, you can use the "Global Star Alignment (deep-sky)" method. Leave the algorithm as Lanczos-4 and interpolation clamping ticked. After registration completes you can now stack the data in the stacking tab. I would recommend the below settings for stacking:

Up to this point I am fine and it is easy enough to follow, I have done script editing so this is all stuff I am familiar with. 

It is the stuff below where we are getting into pixel math where my head starts to hurt.

However, I think I shall give it a whirl first before I start asking for further help as I am keen to learn new methods.

Above you mention that this is a relatively simple operation to carry out with [photoshop, do you know if similar functionality is available within gimp or not?

If you have a video link to the photoshop version I may be able to translate it over to Gimp!

Cheers and thanks for the help thus far, very much appreciate it.

Steve

On 22/10/2023 at 12:56, Stu said:

There are a few calculators around which factor in LP, aperture and a number of other parameters. Mel a Bartels does a lot on this on his site.

https://www.cruxis.com/scope/limitingmagnitude.htm

https://www.bbastrodesigns.com/ObjectContrastCalculator.htm

I can confirm old age is well and truly set in with me. I was going to save the cruxis link to my favourites but when I tried my browser informed me I already had it saved. 

Make way for me an the nursing home 🙄😂

42 minutes ago, Stu said:

There’s another calculator here:

https://www.bbastrodesigns.com/NewtDesigner.html

More info…

https://www.rocketmime.com/astronomy/Telescope/SurfaceBrightness.html

42 minutes ago, Stu said:

Of course, none if this stuff is exact, just gives an indication of what might be visible or not.

And as often happens I have opened an astro Pandora's box 🤣

2 minutes ago, Stu said:

The calculator has an entry for atmospheric extinction which should allow for that.

So it does, my bad missing it. 

Cheers stu

On 18/10/2023 at 17:41, ONIKKINEN said:

But you probably shouldnt stack Ha and Lum to one image if that was what you were planning on, this was just a tip on multiple night/different exposure type work.

Yes the idea of modifying the script had passed my mind but given the above, where do I go from there? 

What program would you use for stacking the data as one or is there another process you could suggest. 

I mean I could use a universal exposure but this leads to other problems too!

This (stacking data) is a science in itself and I am struggling with some of it,  well actually everything 😭🤣🤣

3 hours ago, John said:

Another variable to add to the formula is target altitude. Atmospheric extinction takes it's toll on brightness. There are formulae that help calculate this but they seem quite complex, to my brain at least 🙄

Atmospheric Extinction and Refraction – Asterism.org

Thanks John and @Stu for these. I agree entirely with the altitude being a strong consideration but also and as mentioned by @Mr Spock, localized lp. 

Stu's cruxis.com calculator asks for either brightest star at zenith or sqm at zenith. Now this is great if you have a fairly even sky in all directions, but if like me you have really bad light pollution in one direction but reasonable skies in the other your going to run into issues as you hunt out you object, more so as you drop down in altitude where I think once you get below 45 degrees it gets increasingly problematic. 

So either I stick to one half of my sky or take multiple sqm readings and in doing so add another layer of complexity before even looking at John's atmospheric calculator!

There really is no easy answer to this I am afraid. 

Cheers all 

Steve

12 minutes ago, Stu said:

There are a few calculators around which factor in LP, aperture and a number of other parameters. Mel a Bartels does a lot on this on his site.

https://www.cruxis.com/scope/limitingmagnitude.htm

https://www.bbastrodesigns.com/ObjectContrastCalculator.htm

Thanks Stu,  I shall have a play later on my pc

Ok I know as do most seasoned observers that light pollution has a huge impact on nearly all objects bar lunar and some planetary. I no longer even bother with any local deep sky observing due to light pollution and even narrowband viewing is not particularly rewarding and not really worth the effort. 

Also I have lost count of the number of occasions I could have had impromptu sessions in the back garden when forecast and weather haven't agreed or just a couple of hours of clear weather have graced the evening. It is such occasions I think I need to be taking more advantage of.

So I think I will encourage myself to target more planetary viewing using the 100ED and also think I will join in the 60mm frac double challenge that I have been loosely following on this forum. 

But what I want to know is, what is the guide / formula etc that provides the following:

"magnitude = aperture - bortle less local light pollution" (if indeed such exists)  so I can segment as it were my viewing list(s). 

No doubt similar queries have been thrown out before, and tbh feel I should know better myself but it is  always good to get a fresh take on such things so any help will be gratefully received.

Tia

steve

14 hours ago, LunarRob said:

Hi I have an Orion txt 8 plus and it comes with the below.

Includes a 2" 28mm DeepView eyepiece, 1.25" 10mm Sirius Plossl eyepiece, Shorty 2x Barlow lens

I’ve found that with the 10mm and Barlow I can get a decent look at the planet but they move very quickly for the Dobsonian on std mount and it’s hard to follow with precision I put the big lense on (planet spotter) and get a great wider/longer view of the planets. Is there a better combination and can you get the 10mm and Barlow in 2”?

Thanks

There you have 4 replies and all different and none either right or wrong, it is all a matter of personal taste. 

As you already have a Barlow you have that flexibility already so a fixed length eyepiece could be used to cover your needs we with the added advantage of doubling your focal lengths with said Barlow.

You have not given a budget so @Spile's zoom suggestion is both low priced and very good in quality department.

I personally am a big fan of zooms and if your budget is larger then the baader Mk IV zoom is a superb bit of kit in all departments albeit a little pricey. 

1 hour ago, Coco said:

Thanks Steve, they are in my shopping cart, we have similar bins, I was going to text you but you just answered my question...  

Mine came with an 18mm pair supplied so I bought 10 & 24 to supplement them. I also got some 30mm plossl but these were purchased for the exit pupil size (5mm) as they work well with nb filters. Next I got some 8mm starguiders as these offer the highest recommended useable magnification (x58) without dodging into CA territory of plus 60 but have to say the 24,18 &10 get most usage. The 8's may yet go. 

19 hours ago, Naughty Neal said:

I  have 7, 9  & 18mm all purchased used   for around £60,  lenses all clear no dust or specs showing  in them. 

I was looking at the 24mm uff for a lower power ep with wider view until I saw the 25mm xcel lx, new  on Aliexp delivered for < £57.  Seller had a sale on  - £6 and I  used coupert to get a further discount of another £6 off the total price.

If u ever get the chance of a uff 24, get it. The uff are on another level, I use them in my big bins and my dob, they are superb. 

I recently downloaded the one shot colour stacking script, it is a massive time saver for me and tend to use it. I am preferring it as my go-to now but have a query.

If I grab multiple exposures data at eg 120 seconds with ha filter and 30 seconds at luminance, will it pick up both sets of data and stack or just one?

Tia

Steve

On 28/09/2023 at 15:36, JBadger said:

I don't understand why you felt the need to explain this to me? I didn't say 2" is inherently better than 1.25" nor did I ask to be told what eyepieces I do or don't need, thanks.

Rude

Agreed, I had one of these, still have the 9-27 version and it's a great bit of kit and under budget giving up to x210 which is close to the limit for the 127 anyway. 

https://www.firstlightoptics.com/ovl-eyepieces/hyperflex-72mm-215mm-eyepiece.html