[slartibartfast01]

Interested_observer posted the link to the spreadsheet, it was actually from Pentapixel site - my mistake there.
Astrophotography Nightscape Lens Rating - Google Sheets

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/367178-nig...ns-advice.html

Both spreadsheets use the same formula and have the same scores. They assume that no tracking is used.

[MossyRocks]

Also, is Andromeda really that large? Stellarium shows Andromeda as a tiny spec.

I think I will need to do a composite picture of Andromeda and the moon both taken with my 300mm so people can see the scale of them. But yes Andromeda is huge but really dim compared to the moon or even the bright stars and if visible appears as s dim spot or a slightly larger dim smudge in the sky to the naked eye. What you see is either just the very bright center core or the dimmer but still brighter core region in these cases. The large disk and arms are what makes it huge. With my K-3 and 300mm lens the moon is around 750 pixels across when full and Andromeda is around 2800 pixels across so yes it is about 6x the size.

[MossyRocks]

Also, is Andromeda really that large? Stellarium shows Andromeda as a tiny spec.

Took me a while to get around to doing this but here is an image I took of andromeda using my 300mm lens and K-3 with the moon superimposed in also taken with that same 300mm lens:
The picture of the moon is basically straight out of the camera but cropped and yes it was that color because of the smoke and haze from the fires out west and in Canada. Andromeda on the other side of things was 1.5 hours of total exposure with a lot of processing to bring out the detail.

[Kevin B123]

Took me a while to get around to doing this but here is an image I took of andromeda using my 300mm lens and K-3 with the moon superimposed in also taken with that same 300mm lens:
The picture of the moon is basically straight out of the camera but cropped and yes it was that color because of the smoke and haze from the fires out west and in Canada. Andromeda on the other side of things was 1.5 hours of total exposure with a lot of processing to bring out the detail.

Thanks for taking the time to put this together.
I'm just surprised it is that big, but wow 1.5 hrs exposure time - I half imagined say 10 minutes would catch it. That's off my charts for now, I will keep with MW / foreground shots or planets for a while.

[MossyRocks]

I'm just surprised it is that big, but wow 1.5 hrs exposure time

I am in an extremely light polluted area so to be able to bring out any detail I need to have a lot of shots to drive the noise way down so that I have a hope of separating the details from the sky glow. I also do not have any long term accurate tracking (only astrotracer) so with that I need to use a higher ISO to make up for having shots that are only 20 seconds long which only worsens the noise problem.

My backyard is in a very bright Bortle 8 area so that fact that I can manage to find some of these things seems impressive. If you look at some of what the masters over in the astrophotography group are able to do they are using total exposure times usually starting at an hour with some approaching a full day (yes 24 total hours of exposure) and they have some really nice tracking mounts. I always refer people to this image from Pete_XL with just over an hour of exposure and he is in a Bortle 5 area and has a proper equortorial mount.

I half imagined say 10 minutes would catch it

Depending on where you are you could start to get something good at 10 minutes. I think I could at my lake which is a very dark Bortle 3 area but the sky has never cooperated when I am up there. This winter it will be nice as I can just go out on the ice and shoot unobstructed in some cold clear skies which should produce some great results.

[Kevin B123]

Depending on where you are you could start to get something good at 10 minutes. I think I could at my lake which is a very dark Bortle 3 area but the sky has never cooperated when I am up there. This winter it will be nice as I can just go out on the ice and shoot unobstructed in some cold clear skies which should produce some great results.

I can get to a Bortle 4 site in around 40 minutes from home, weather and moon dependant. My problem is I have two cameras and tripods and want to maximise the time available, and never really do justice to the subject in hand. Doing 21mm and 200 mm is not really working, I just need to decide which and take one camera, and both lenses just in case. I'm going to plan for the next shot for Andromeda only and really try for that, using a mask for sharpness and let astrotracer blast away at it.

[MossyRocks]

I'm going to plan for the next shot for Andromeda only and really try for that, using a mask for sharpness and let astrotracer blast away at it.

That will fit nicely in the frame, but I suggest recomposing every 5 or 6 shots to keep it properly in the frame. With a 200mm you should be able to do 30 second exposures with astrotracer. I do 20 second ones of Andromeda with a 300mm lens.

[Oktyabr]

This thread inspired me! I sold my K-70 and ended up with a lightly used K3ii. Tonight was supposed to be my first clear, moonless night to play with it but clouds snuck in under the radar and messed up most of my dreamed of shots. At least I can testify that the built in GPS/Astrotracer in the K3ii is worth the money. I shot a few at 60 seconds with my 100 2.8 WR Macro and one at 90 seconds with an old M50 1.7, with very little trailing in either example. What I am interested in is knowing what technique do I need to perfect to get the stars sharp and not just round blobs of light? I suspect it's a focus issue or is it just brighter stars blobbing out on longer exposures? If that's the case would I be better off stacking a bunch of shorter shots? Or is this just really bad coma and I need to stop it down some? I REALLY want to put my 55-300 PLM to work on Andromeda and the usual suspects in the Orion.

A few examples of my FIRST night out trying this, so please, don't giggle to loudly.

Pleiades peaking through the clouds for just a minute. 60 sec, 50mm, f/1.7, iso 400




Same 50mm f/1.7, 20 sec, iso 400

[MossyRocks]

This thread inspired me! I sold my K-70 and ended up with a lightly used K3ii. Tonight was supposed to be my first clear, moonless night to play with it but clouds snuck in under the radar and messed up most of my dreamed of shots. At least I can testify that the built in GPS/Astrotracer in the K3ii is worth the money. I shot a few at 60 seconds with my 100 2.8 WR Macro and one at 90 seconds with an old M50 1.7, with very little trailing in either example. What I am interested in is knowing what technique do I need to perfect to get the stars sharp and not just round blobs of light? I suspect it's a focus issue or is it just brighter stars blobbing out on longer exposures? If that's the case would I be better off stacking a bunch of shorter shots? Or is this just really bad coma and I need to stop it down some? I REALLY want to put my 55-300 PLM to work on Andromeda and the usual suspects in the Orion.

A few examples of my FIRST night out trying this, so please, don't giggle to loudly.

Pleiades peaking through the clouds for just a minute. 60 sec, 50mm, f/1.7, iso 400




Same 50mm f/1.7, 20 sec, iso 400

I wouldn't make fun of someone's first attempt, or any attempt. Everyone has to start somewhere and asking questions and for feedback is always a good thing.

More than likely it is a focus issue combined with the lenses being wide open. With my still limited experience I have found that lenses that in normal shooting are good lenses can show all their weaknesses with ease when doing astrophotography. I found this out with my Series 1 Vivitar 135mm f/2.3 which was a bit disheartning given how well that lens does under more normal conditions. Basically if you don't have a proper equatorial you will be stacking, and even if you do have an equatorial there are benefits to stacking.

I would say that for your exposure time your ISO is good enough but stop those lenses down 1 or 2 stops. I shoot my 300mm f/4 at f/5.6, ISO 400, and 20 seconds when going after M42 (the Orion nebula) and M45 (the Pleiades) from my backyard with a red intensifying filter (I've only been out twice since I got it because of weather but it gives some great improvements). For dimmer things like M31 (the Andromeda Galaxy) I will crank things up to ISO 1600 but I will probably shoot it at ISO 800 when I try again or even ISO 3200 for really dim things like M51 (the whirlpool galaxy). Basically for the dim things I am trying to get the object visible just above the noise floor on a test image while maintaining as much dynamic range as possible.

For your 55-300mm and 100mm macro I would suggest making a bahtinov mask for each of them, use that for focusing, and stop them down 1 if not 2 stops. For the 50mm focus using magnified live view without focus peaking, get the stars as small as possible and then stop it down to between f/4 and f/5.6 to paper over the coma and any missed focus. Focusing is best done on a really bright star, I like using Sirius, Rigel, or any of the other really bright stars that are super easy to find. However be careful to not use a planet as they don't provide good results, especially with a bahtinov mask.

[Oktyabr]

I didn't even think about stopping down when I went out last night but yeah, that would explain a lot of the coma. I also wonder about UV filters? Could they be a serious problem for extended night time exposures? I plan to experiment myself the next night I go out but I forgot I even had one on last night. I am in a Bortle Class 4 area but get to shoot into a Class 1 as I live right on the Pacific coast. I'm habitual about keeping UV filters on to protect against blowing sand and salt water spray but if it's a true problem for night shoots I may have to remove it.

[Posse96]

Good overview. I've been shooting landscape & wildlife for years (well, everything for years, but love outdoors the most). I embarked on star shooting last year. I'm using a K-3 Limited. I've found having something int he foreground always adds to the dramatics. I took pics of my Cam settings with the photo on the cam screen to give some perspective. Highly recommend tripod or bean bag and used the Pentax GPS unit


For the Milky Way, here are (2) shots

Cam - Pentax K-3 limited
Lens - Sigma 20mm f/1.8 EX DG RF Aspherical Wide Angle Lens - Love this lens!

Access - Pentax GPS OGPS-1 Astrotracer & Pental F-Control Remote


First Shot

ISO 6400

F-Stop: 3.5
Exposure 10 secs


Second Shot

ISO 6400
F-Stop 3.5
Exposure 20 secs

These were taken at June Lake CA. I personally feel 20 secs is the sweet spot for Milky Way. The Astrotracer did well to eliminate star trail. Of course, star trail can be dramatic and simply remove the tracer and go for a nice 30 sec - 2 min shot.


This realm is still new to me, so this thread is great resource. I look forward to shots this June at June Lake; Anza Borrego State Park (in CA) is so dark, night shooting is intense.

[Kevin B123]

I think with the software available now (deep sky stacker, Sequator etc.) any decent camera, a bit of patience and effort can yield good results. I got good results from the K-50 before and I have seen others have too. Lately shooting wider with foreground has been more successful than deeper sky as I just can't get the targets properly, or just not honed the technique at least.

I am starting to develop a check list for stuff to take too, so I don't forget crucial things.

Even then I went out recently with three cameras and two tripods and left one tripod in the car, I did take a near useless camping stool, didn't need that.

[MossyRocks]

I also wonder about UV filters? Could they be a serious problem for extended night time exposures?

Take them off they are only hurting your image quality at night. The only filters I would recommend would be either a real narrow band light pollution filter (big bucks great results), or a red intensifying filter (the poor man's light pollution filter). A specialty light pollution filter used for actual astronomical observation will block almost all of the really bad light pollution and little else. They also are usually optically better so don't degrade the image quality much at all. A red intensifying filter will block a good portion of the light pollution but unfortunately aren't as narrow band as real light pollution filters so they will block some of the other good useful wanted light. They also aren't as optically great as real light pollution filters. However the decrease in light pollution substantially outweighs the decrease in image quality so you will still get substantially better results. It was almost shocking how much better my M42 (orion nebula) pictures got by sticking one in front of my 300mm. Expect much better contrast and detail in deep sky objects, these get washed away by the light pollution, and a big reduction in sky glow. It was good enough that I decided that all my old astro images I took with that 300mm needed to get binned. As in a single frome shot from my back yard gave better results than a stack of 10 minutes worth of shots from the near by dark area. I do live in an area that has a massive light pollution problem so your results may not be as dramatic but you should expect a good increase. Now I am just waiting for it to stop snowing, have clear skies, and to not have to work the next day.

[MossyRocks]

I am in a Bortle Class 4 area but get to shoot into a Class 1 as I live right on the Pacific coast.

I should remember to check what I am responding to before submitting as I wanted to say more. Now I am jealous I am in a very bright Bortle 8, the dark place near by is a bright Bortle 5 with a 45min drive and it is a 2hr15min drive to a dark Bortle 3. Given your location a light pollution filter won't provide as dramatic results but will be of most benefit when shooting from your home, or shooting towards civilization near the horizon from you Bortle 1 spot(s) and don't expect as dramatic improvements as I got with one. Some day I will make it out to some very dark places but the nearest ones to me require driving almost to Canada, or way into Iowa. Maybe this summer if I am out in Colorado I can go way out into the mountains some night and enjoy shooting through less atmosphere that is drier in a super dark spot.

[biz-engineer]

In most posts of this thread supposed to be a guide to astrophoto, 20 seconds or 30 seconds exposures times are used at ISO around 3200 and 6400. Those settings aren't best. Pentax astrotracer with slow shutter speed noise removal can deliver best quality between 2 minutes and 4 minutes of exposure, that's 4 stops lower ISO => something like ISO800.