[BAA Comets] Profitability of northern sky surveys -- anymore?

[rmiles at baa.u-net.com]

Amar, 

Thanks for the questions. 

As an example, about 5 years ago, I ran a comet search from my home in
the UK for about 18 months using an f/2.8 0.106-m refractor and
monochrome CCD camera that allowed me to detect comets down to mag 16
using 60-s exposures. Three sets were taken each about 40 minutes apart
- all in the evening sky after sunset. Although 3 known comets were
detected, as well as a distant artificial satellite, I did not discover
any new object of course! 

I have since checked what would have happened if I had kept up searching
and the answer is that I still would not have discovered a comet! One
reason is that observations before sunrise are more likely to find new
comets by about a factor of 3 compared with the evening sky. Some
amateurs have found 'morning' comets in recent years. Another reason is
that since the UK is in the northern hemisphere, the surveys trawl this
region of the celestial and find approaching comets when they are very
faint, and so little if anything is left to be discovered. The same is
true of asteroids brighter than mag 19. 

I did give the 2017 George Alcock Memorial Lecture on the subject of
comet discoveries from the UK and do intend to write this up at some
point. I have kept a spreadsheet of amateur discoveries made during the
past 20 years as part of that research. The UK weather does not help
when it comes to conducting surveys because of the small number of clear
nights especially if the area of searching is low in the sky after
sunset. 

Concerning your question: "If you -- amateur sized surveys -- are to
hunt for undiscovered objects from where you are -- above +30* -- then
what are your likely targets going to be from the genres available?
Comets. Main Belt Asteroids. Near Earth Asteroids. Supernovae. Novae.
Variable Stars. Some other Transient Objects." 

Surveys that look for moving objects differ from surveys that find new
'stationary' objects. The latter are more likely to be successful.
Computerisation of many of the tasks involved would also be required to
increase the chance of success. A different observing strategy is also
generally required for the different classes of object that you mention,
so that also makes life difficult. 

One new suggestion for observational work is to detect serendipitous
occultations of stars by objects in the Edgeworth-Kuiper Belt. This
would require two observers living within a few km of each other (or two
widely separated telescopes) to video monitor the same patch of sky
searching for disappearance events as say a 5-50 km size object happened
to occult a field star. Computer analysis of the field would detect the
drop out of light - it would be impossible to check this visually. 

With all these surveys, the amateur has a great disadvantage by way of
the 'etendu' of their optical system compared to those used by
professionals. Basically fast focal ratios and larger apertures are
needed, which means great expense! 

Hope this is all not too discouraging. 

Richard Miles, BAA 

On 2019-03-03 10:24, amar sharma wrote:

> Hello BAA Comet members, 
> 
> I wish to learn of a question from you. This is on Sky Surveys. 
> 
> The last I was in touch in depth on this topic was over half a decade ago (when working vehemently on comet history, if some of you recall). So I'm out of touch on the developments -- and shut downs -- that have happened on the sky survey front in the by-gone recent years. 
> 
> What has changed since half a decade ago? Pan-STARRS. Just now came to know of ATLAS. And? 
> 
> Generally speaking, with so many -- as ever -- sky surveys around in the northern hemisphere and the still-incompetent ratio with the southern hemisphere, what is the status of patrolling going on in the northern hemi.? Is it going to reach a saturation level anytime, disregarding the fact that newer minor planets will keep appearing and being discovered from what are actually existing? 
> 
> What is the utility of a northern hemisphere sky survey being established as of 2019, say until 2025? Is it of any useful value if any new northern surveys are constructed? Or should the focus go southern? And what if the surveys are amateur sized, i.e. 16-24 inches with sensitive CCDs? My intention of asking is not of professional sized surveys (>0.75-1-meter) but of amateur ones. 
> 
> Just asking. 
> 
> Next question. If you -- amateur sized surveys -- are to hunt for undiscovered objects from where you are -- above +30* -- then what are your likely targets going to be from the genres available? Comets. Main Belt Asteroids. Near Earth Asteroids. Supernovae. Novae. Variable Stars. Some other Transient Objects. 
> 
> Its understood that the thrust of working the survey is "to enjoy the journey more than the destination", i.e. happy if you get some new under your belt, but even happier to be out each night attempting sleuthing. 
> 
> Thank you. Regards, Amar. 
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