[Aavso-photometry] Transient nebula in Lyra???

[Vello Tabur]

Jim Roe wrote:
> One of our local club members was imaging M57 in Lyra recently and one 
> of his images seems to show a planetary nebula at the location of RX 
> Lyr.  An image 8 days later shows no nebula but a bright red star. 
> Looking at the AAVSO data base, it would appear the RX Lyr is very close 
> to its current maximum so that part should be no surprise.
> 
> Would some of you take a look at his images at
> 
> <http://asemonline.org/archives/category/members-pages/jim-melkas-pages/deep-sky-images/> 
> 
> 
> and let us know if there is any actionable intelligence here?
> 
> Jim Roe [ROE]

Hi Jim,

This is often caused by chromatic aberation. Miras radiate most of their 
energy in the IR and become bluer when they brighten, thus reaching 
focus. I noticed this several years ago using a camera lens + CCD. To 
test this, I refocused the lens using the IR mark and found that the 
blurry Miras came into focus while the other field stars became defocused.

Vello