M101 newbie

[ninjageezer]

Ok so i hope to try to image M101 this coming week,

Kit.

HEQ5 belt modded mount 

william optics zenithstar 73 

william optics 50mm guide scope 

ZWO 120mm mini guide cam

Astro modified canon 60d.

 

i will be using NINA and PHD2 .

bortle 5 skies.

 

i have spent the last couple of weeks testing and getting to know the kit a bit first .

i am trying to get some starters for sub lengths and iso.

i was thinking 180 sec iso 800 ?

i tried some guiding tests last week and was getting an average of 0.6-0.7 

any pointers will be much appreciated.

[PeterCPC]

I think that you will need longer exposures. M101 is quite feint and a difficult target. I would try at least 300 secs exposure if you can do that.

[Nik271]

My modest experience from Bortle 5 sky is that in very long exposures the glow from the sky swamps the fine detail. Plus the longer the exposure the higher the risk of cloud/wind/satellite ruining the sub. 180 seconds may be about right.

I had good results with just 30 second exposures and 150mm Newtonian at F/5 with an unmoddded Canon 250D but that was a bit on the short side.

[woldsman]

If you are using NINA, there is an optimal exposure time plugin available. 

[The Lazy Astronomer]

With the information you've provided, your optimum minimal exposure time is likely to be in the range of 1 - 2 minutes; this is the point at which your sky background swamps your sensor read noise.

Based on that, your plan to go with 3 minute subs should be fine, but if you find you're having tracking/guiding issues, you can safely lower the exposure time a bit without compromising the image. 

[ninjageezer]

thanks guys 😃

[ninjageezer]

First time out tonight with new kit ,thought i would try the three point polar alignment plugin, but kept getting the error in the attached photo .

the mount seemed to move to the first 2 locations no bother ,it was the 3rd when the error appeared and i noticed the mount only moved a tiny bit then stopped .could the mount have moved to its limit ?

i tried adjust as per tips in the error box.

Edited March 30, 2022 by Cornelius Varley
background colour removed