bomberbaz

6 hours ago, Lee_P said:

Tighter bandwidths do make a difference. See my review of some dualband filters here for examples. The Optolong L-Ultimate is possibly the best available right now (Ha / OIII dualband, 3nm) but it's 2" only and expensive!

Great review Lee. If I had a bottomless wallet it would be the L-ultimate, shame they don't do a 1.25"! 

However the Askar dual band is a compelling buy at that price and performance. 

Thanks for bringing it to my attention.

Steve

Hello all.

I currently use this ZWO dual band  Filter when imaging nebula and the details can be found at the link. This has a fairly high bandwidth of 15nm in HA and stated transmission of "over" 80%. I don't like this because this could vary from 80.01 to 89.99, a considerable difference but that's another story.

I was wondering if adding more data to an hydrogen rich image using a tighter bandwidth filter is worthwhile consideration with the OSC camera (It's the ZWO 183 MC Pro ) ZWO 1.25" Ha 7nm Narrowband Filter | First Light Optics

Has anyone tried this and had any success ?

cheers

steve

I think given your gear and its limitations, that is a fantastic image

Not sure where to post this, so if it isn't the right place then please feel free to relocate admins.

I did a brief session with the eVscope tonight, tried a spot looking S\W from my garage, (,least LP) just had to be careful not to trigger a myriad of security lights in the area! (Cats got me twice).

I decided to try something a little harder than the messier's, opting for IC 342 galaxy. Quite a difficult face on object.

Grabbed a total of 20 minutes of data in short bursts totalling 7 images. They are not timed as in traditional imaging and you can tinker with brightness and contrast on the fly.

Anyway, I was transferring the data files to my one drive and decided to see if DSS was available to use on the android system ( which it Isn't) to see what's out there really, but I found an APP which is named Eagle images stacker. Only cost a fiver so thought wth, let's see what a basic tablet and a little imagination can do!

Had an initial play, then used my tablet image editing software and managed something not bad for 20 minutes. 

Top one is the stack, second with a brief tinker at processing using Google pictures app. I know it's not Photoshop quality, far from it but it gives me some satisfaction. 

On 15/02/2023 at 13:18, Stu1smartcookie said:

seems like you are losing your head in one of those photos Magnus 

 

Also nearly the cat 😺🤯

I have used a cable similar to this although it's 5 metres.

Cable. It isn't a powered cable, but I have streamed video with it although as yet not recorded high speed video. 

UPDATE.

Correcting first off my previous statement that these are F2.6, I think that is not correct and do not know the correct F ratio despite much searching however they are probably around F6.

I spent half a day on birding, looking in trees of course and chromaticity is apparent but not excessive. I guess it depends what is acceptable to you. 

WHat I did also do was follow an incoming passenger plane faultlessly and also managed to easily track a helicopter at great height where because of the stability, was able to identify it as a police one. 

Reviews here. Amazon reviews need scrutiny though, they have been known to be somewhat suspect.

https://www.amazon.co.uk/Binoculars-2-1x42mm-Waterproof-Stargazing-Atronomy/dp/B0822QRLKJ

Ok so really not sure if this is right but here was my calculation as there isn't a focal length on Bressers website for my bins.

They are 16x42 which gives a 2.6 exit pupil. 

Devide objective by exit pupil gives F ratio 16\2.6=6.1.

Is this correct or am I barking up a wrong un?

I have a 10x30 pair, used them a fair bit for astro. What they lack in aperture is made up for by the stability. 

1 hour ago, AstroNebulee said:

I have the rotator just to help framing some targets and because it's an all screwed imaging train and I like the 294mc pro orientation in landscape to my scope tube if that makes sense, so the longest side of the sensor is aligned to the top of my scope. (just my ocd I guess) . I've only rotated it once on the soul nebula but never captured enough data on it. Every other target has fitted in perfect, (M31 not rotated attached) I use the RVO rotator as it has less wobble when the thumbscrews are undone to rotate than the skywatcher one has. It's just much better. 

Lee 

 

Had another look at the 72ED and won't bother with the rotator. I rarely rotate anyway but if I need to simply slacked the tube rings. Think that will suffice here too and the less parts on the focal train, the better imho.

Going to have a good think about all my gear next, I simply have too much and need to scale down before I get the 72ED.

Thanks Lee. Glad you put that in. Never knew I also would need a rotator too. 

12 minutes ago, AstroNebulee said:

Yep I have the 2 inch filter drawer in my setup. I'll attach an image of my setup and a diagram of the components. I still have a little bit of focus tube travel so all ok. I have the elastic band on the filter drawer just as added security for the drawer but the magnets are sufficient enough. 

Lee 

42 minutes ago, AstroNebulee said:

I use the 72ed on az gti with an zwo asi294mc pro. The amp glow isn't an issue and is so easily calibrated out and I've never seen it on my images. You do tend to get more star bloat with the 72ed but with filters an Astronomik L3 in my case, the stars are tight. (Attached my recent images) 

Lee 

 

Thanks Lee. Is there enough room in the focus to accommodate a filter drawer. https://www.firstlightoptics.com/zwo-accessories/zwo-2-filter-drawer-m42-m48-v2.html

23 minutes ago, Elp said:

I suspect you're after the focal length.

Not exactly sure what you mean by this although I know increasing or decreasing this affects performance both ways.

What I have with the evoguide has served its purpose in getting me into imaging, now I just want to step it up a little.

As you know it is married up to the az GTi so in my efforts to improve performance, I must be wary of weight as I have no wish or intention for that matter of upgrading my mount. The 72ED seems to have the perfect compromise of weight and hopefully performance.

I have now forgot what point I was trying to make here 🤣

Anyway, seems it will work so just need to look at finance 😭 haha

48 minutes ago, Elp said:

I think you'll see a massive difference going up in aperture from the evoguide. From my experience aperture makes a difference, the thing you'll notice more is the resolution difference. If you can bin the camera or get a larger pixel one that will also speed up signal capture. Never really binned the 183, but I know the 294 performs better in terms of signal acquisition.

Note, you'll still be imaging 4-8 hours per image at least unless it's one of the bright common targets. More time will be better if you've got the patience.

I have been looking at the 533mc, seems to marry up ok when running it through this and has no amp glow   https://astronomy.tools/calculators/ccd_suitability

Last time of gathering data on deerlick group, the total data grab was 7 hours so happy putting in the time.

Ok been thinking for a while about upgrading my imaging telescope to increase aperture, reduce image size and reduce integration time.

Current gear Evoguide +FF and zwo183MC osc. Evoguide supposedly 240 fl (F4.8) but ASIAIR reports it as 267fl which would give F5.34. 

I do not know if this if this is accurate but assuming it is, it makes things less complicated.

Anyway, I was thinking of getting the SW 72ED + a FF that leaves it at it's native focal length of 420 F5.8.

I have calculated (assuming the evoguide fl is 267) and the 72ed is true to its stated fl, that the 72ed will gather data at around 1.25 the speed of the evoguide, all other things being equal.

Both ota should be ok with regard to sampling from my back garden.

Am I missing anything here?

EDIT

Further to the above, I have it at a 1/3 improvement for the 72ed over the evoguide but only about 8% if the fl of the evoguide is actually 240. !🙄 

15 minutes ago, vlaiv said:

And is unfortunately incomplete explanation.

F/ratio is not measure of the speed of the system (as it omits one more component that can change and that is pixel size).

Right but it does explain to me the barlow 2x/4x issue which for a long time, had me confused. No longer.

TBH I find much of it confusing, I guess I have not got a great head for maths. 

On 19/01/2011 at 23:16, Luke said:

It took me over a year to work that one out! I was fairly convinced that a huge aperture F10 SCT would image faster than a small aperture, fast scope. But the penny finally dropped a few weeks back.

Here's how it makes sense to me, please correct me if I am wrong:

Ignoring things such as differences in contrast, take these two scopes:

1) 80mm refractor, focal length 500mm, fairly fast at F6.25.

2) 280mm SCT, focal length 2800mm, slow at F10.

Penny drop #1:

At prime focus - no barlows, reducers, ... - how zoomed in you are on an object depends on the telescope's focal length, nothing else. A bit like on a camera's 50-300mm zoom lens, 300 gets you in way closer than 50.

So at prime focus, objects look 5.6 times bigger in the SCT (2800mm / 500mm).

Penny drop #2:

When you switch from prime focus to using a 2x barlow to double up the image size, the amount of time you need to get the same brightness of image is not double, it is FOUR times as long an exposure.

A bit like if you have an image in Photoshop, such as 100x100 pixels, if you double it up in size, it actually takes up four times as many pixels (100x100 = 1000, versus 200x200 = 4000).

Penny drop #3:

Although the SCT has over 12 times the light grasp of the 80mm refractor (280mm squared / 80mm squared), objects are 5.6 times bigger in the SCT, which works out that they cover over 30 times as many pixels (5.6 * 5.6).

12 times more light versus sharing the light over 30 times as many pixels - that's why the SCT needs a longer exposure - 12 times more light in, but spread over 30 times the number of pixels.

Final penny drop:

Of course, while the refractor is faster, it is nowhere near as zoomed in at prime focus. Imagine if your target needs the zoom of the SCT. To get the equivalent zoom in the 80mm, you'd need to use something like a 5x barlow,which would take 5x5 = 25 times longer to expose than the usual prime focus exposure. So if you are using an SLR in particular and want to get in close on small targets, the SCT could come into its own then, this is presumably why some imagers use a refractor for bigger targets and the SCT for the small, faint things.

I have been trying to get my head around this myself for some time, finally I have found an explanation that tells it in my language that I can relate to !

10 hours ago, AstroKeith said:

You will note that those above suggesting lasers are in the USA. Lasers in the UK are more problematic.

a) Our air traffic density is higher. Also so is our population density, so more likely for someone to 'report' you.

b) The 'new' legal max power in the UK is 1mW. Anything beyond that (ie the 5mW often sold) require very careful use (formal training and sign offs, etc) to not fall foul of the Health and Safety legislation. 

c) No UK event will allow you to use one.

Actually not all are from the USA, I am UK based. 

I bought my laser from Optic Star a few years back, certainly after the last changes to laser guidance was made. Unless that is changes have been made that I am totally unaware of, however I have not been able to find anything.

A laser is pretty much the same as any other dangerous tool such as a chainsaw or angle grinder, safe when used correctly & with care. Mine is not left on all the time and like others have alluded to it is flicked on, then move scope to area of interest, flick off and then centre with my RACI. The usual burn for want of a better description is  I would guess around 5 seconds.

The guidance for using lasers is quite lengthy and well worth a read "laser safety advice".  I believe my laser falls within safety guidelines and I will continue to use it "with care".

Plus 1 more here for a laser. Much more fun to use and as others have pointed out, I too find it much easier to use than a telrad or similar.  It is also used in conjunction with a RACI.

breathtakingly beautiful. Just take a little time looking and considering the size of it, bonkers and beautiful. 

Ok did a play with images above of @alexbb & @tomato then blended them together, think it looks pretty neat. Hope you don't mind. 

39 minutes ago, alexbb said:

Regarding your original question - have you tried to remove the stars after a stretch?

A 5 minutes play in PixInsight with the XTerminators + LHE and MLT can easily reveal some additional signal and details. Spending more time can improve the outcome, of course.

Have to say that is a pretty sweet image indeed. Well done.

It's the star processing side that really interests me in Pixinsight, although the entire package is rather compelling.

If I do get into imaging in a more meaningful  manner, I may indulge myself. 

I had a chance to have a quick play around with this, data as mentioned seems pretty decent. 

So I used Siril for the main work and then tweaked in Gimp. I didn't go mad with the stars, and tried two versions with the lower version adopting a less is more approach.

3 hours ago, CraigD1986 said:

Thanks all for the input. I do own the Astronimik L3 but used the L-enhance as this was a hydrogen rich target. Maybe I’d also be better off using shorter exposures to control the stars a bit (maybe 120 or 180 seconds). If I got the same total exposure time but using shorter single subs, would I get the similar results to using 5 min subs?

The L3 is purely a IR/UV cut filter, the L-enhance is for filtering your ionised gas lines in H and OIII so they are not doing the same thing. You should stack the filters. I have the L2 version and it is permanently fitted to my set up to avoid bloating.

Regarding the star shapes, I had this once and it was actually the tracking in RA that was shown to be the fault (I use ASI AIR btw), once I tweaked this I got my stars nice and round again.